Elements of Structural and Systematic Botany Part 19

_F_, part of the inflorescence of spikenard, _Aralia_ (_Araliaceae_), 1. _G_, a single flower of the same, 3. _H_, the fruit, 2. _I_, cross-section of the _H_. _J_, inflorescence of dogwood, _Cornus_ (_Corneae_). The cl.u.s.ter of flowers is surrounded by four white bracts (_b_), ?. _K_, a single flower of the same, 2. _L_, diagram of the flower. _M_, young fruit of another species (_Cornus stolonifera_) (red osier), 2. _N_, cross-section of _M_.]

The last and highest group of the _Choripetalae_, the _Calyciflorae_, embraces a very large a.s.semblage of familiar plants, divided into eight orders and thirty-two families. With few exceptions, the floral axis grows up around the ovary, carrying the outer floral leaves above it, and the ovary appears at the bottom of a cup around whose edge the other parts of the flower are arranged. Sometimes, as in the fuchsia, the ovary is grown to the base of the cup or tube, and thus looks as if it were outside the flower. Such an ovary is said to be "inferior"

in distinction from one that is entirely free from the tube, and thus is evidently within the flower. The latter is the so-called "superior"

ovary. The carpels are usually united into a compound pistil, but may be separate, as in the stonecrop (Fig. 111, _E_), or strawberry (Fig. 114, _C_).

The first order of the _Calyciflorae_ (_Umbelliflorae_) has the flowers small, and usually arranged in umbels, _i.e._ several stalked flowers growing from a common point. The ovary is inferior, and there is a nectar-secreting disc between the styles and the stamens. Of the three families, the umbel-worts or _Umbelliferae_ is the commonest. The flowers are much alike in all (Fig. 110, _A_, _B_), and nearly all have large, compound leaves with broad, sheathing bases. The stems are generally hollow. So great is the uniformity of the flowers and plant, that the fruit (Fig. 110, _D_) is generally necessary before the plant can be certainly recognized. This is two-seeded in all, but differs very much in shape and in the development of oil channels, which secrete the peculiar oil that gives the characteristic taste to the fruits of such forms as caraway, coriander, etc. Some of them, like the wild parsnip, poison hemlock, etc., are violent poisons, while others like the carrot are perfectly wholesome.

The wild spikenard (_Aralia_) (Fig. 110, _F_), ginseng, and the true ivy (_Hedera_) are examples of the _Araliaceae_, and the various species of dogwood (_Cornus_) (Fig. 110, _J-N_) represent the dogwood family (_Corneae_).

The second order (_Saxifraginae_) contains eight families, including a number of common wild and cultivated plants. The true saxifrages are represented by several wild and cultivated species of _Saxifraga_, the little bishop's cap or mitre-wort (_Mitella_) (Fig. 111, _D_), and others. The wild hydrangea (Fig. 111, _F_) and the showy garden species represent the family _Hydrangeae_. In these some of the flowers are large and showy, but with neither stamens nor pistils (neutral), while the small, inconspicuous flowers of the central part of the inflorescence are perfect. In the garden varieties, all of the flowers are changed, by selection, into the showy, neutral ones. The syringa or mock orange (_Philadelphus_) (Fig. 111, _I_), the gooseberry, and currants (_Ribes_) (Fig. 111, _A_), and the stonecrop (_Sedum_) (Fig. 111, _E_) are types of the families _Philadelpheae_, _Ribesieae_, and _Cra.s.sulaceae_.

[Ill.u.s.tration: FIG. 111.--_Calyciflorae_ (_Saxifraginae_): _A_, flowers and leaves of wild gooseberry, _Ribes_ (_Ribesieae_), 1. _B_, vertical section of the flower, 2. _C_, diagram of the flower. _D_, flower of bishop's-cap, _Mitella_ (_Saxifragaceae_), 3. _E_, flower of stonecrop, _Sedum_ (_Cra.s.sulaceae_), 2. _F_, flowers and leaves of hydrangea (_Hydrangeae_), . _n_, neutral flower. _G_, unopened flower, 2. _H_, the same, after the petals have fallen away. _I_, flower of syringa, _Philadelphus_ (_Philadelpheae_), 1. _J_, diagram of the flower.]

The third order (_Opuntieae_) has but a single family, the cacti (_Cactaceae_). These are strictly American in their distribution, and inhabit especially the dry plains of the southwest, where they reach an extraordinary development. They are nearly or quite leafless, and the fleshy, cylindrical, or flattened stems are usually beset with stout spines. The flowers (Fig. 112, _A_) are often very showy, so that many species are cultivated for ornament and are familiar to every one. The beautiful night-blooming cereus, of which there are several species, is one of these. A few species of p.r.i.c.kly-pear (_Opuntia_) occur as far north as New York, but most are confined to the hot, dry plains of the south and southwest.

[Ill.u.s.tration: FIG. 112.--_Calyciflorae_, _Opuntieae_ (_Pa.s.siflorinae_).

_A_, flower of a cactus, _Mamillaria_ (_Cactaceae_) (from "Gray's Structural Botany"). _B_, leaf and flower of a pa.s.sion-flower, _Pa.s.siflora_ (_Pa.s.sifloraceae_), . _t_, a tendril. _C_, cross-section of the ovary, 2. _D_, diagram of the flower.]

The fourth order (_Pa.s.siflorinae_) are almost without exception tropical plants, only a very few extending into the southern United States. The type of the order is the pa.s.sion-flower (_Pa.s.siflora_) (Fig. 112, _B_), whose numerous species are mostly inhabitants of tropical America, but a few reach into the United States. The only other members of the order likely to be met with by the student are the begonias, of which a great many are commonly cultivated as house plants on account of their fine foliage and flowers. The leaves are always one-sided, and the flowers moncious.[13] Whether the begonias properly belong with the _Pa.s.siflorinae_ has been questioned.

[13] Moncious: having stamens and carpels in different flowers, but on the same plant.

[Ill.u.s.tration: FIG. 113.--_Calyciflorae_ (_Myrtiflorae_, _Thymelinae_).

_A_, flowering branch of moosewood, _Dirca_ (_Thymelaeaceae_), 1. _B_, a single flower, 2. _C_, the same, laid open. _D_, a young flower of willow herb, _Epilobium_ (_Onagraceae_), 1. The pistil (_gy._) is not yet ready for pollination. _E_, an older flower, with receptive pistil. _F_, an unopened bud, 1. _G_, cross-section of the ovary, 4. _H_, a young fruit, 1. _I_, diagram of the flower. _J_, flowering branch of water milfoil, _Myriophyllum_ (_Haloragidaceae_), . _K_, a single leaf, 1. _L_, female flowers of the same, 2.

_M_, the fruit, 2.]

The fifth order (_Myrtiflorae_) have regular four-parted flowers with usually eight stamens, but sometimes, through branching of the stamens, these appear very numerous. The myrtle family, the members of which are all tropical or sub-tropical, gives name to the order. The true myrtle (_Myrtus_) is sometimes cultivated for its pretty glossy green leaves and white flowers, as is also the pomegranate whose brilliant, scarlet flowers are extremely ornamental. Cloves are the dried flower-buds of an East-Indian myrtaceous tree (_Caryophyllus_).

In Australia the order includes the giant gum-trees (_Eucalyptus_), the largest of all known trees, exceeding in size even the giant trees of California.

Among the commoner _Myrtiflorae_, the majority belong to the two families _Onagraceae_ and _Lythraceae_. The former includes the evening primroses (_nothera_), willow-herb (_Epilobium_) (Fig. 113, _D_), and fuchsia; the latter, the purple loosestrife (_Lythrum_) and swamp loosestrife (_Nesaea_). The water-milfoil (_Myriophyllum_) (Fig. 113, _J_) is an example of the family _Haloragidaceae_, and the _Rhexias_ of the eastern United States represent with us the family _Melastomaceae_.

The sixth order of the _Calyciflorae_ is a small one (_Thymelinae_), represented in the United States by very few species. The flowers are four-parted, the calyx resembling a corolla, which is usually absent.

The commonest member of the order is the moosewood (_Dirca_) (Fig. 113, _A_), belonging to the first of the three families (_Thymelaeaceae_). Of the second family (_Elaeagnaceae_), the commonest example is _Shepherdia_, a low shrub having the leaves covered with curious, scurfy hairs that give them a silvery appearance. The third family (_Proteaceae_) has no familiar representatives.

The seventh order (_Rosiflorae_) includes many well-known plants, all of which may be united in one family (_Rosaceae_), with several sub-families. The flowers are usually five-parted with from five to thirty stamens, and usually numerous, distinct carpels. In the apple and pear (Fig. 114, _I_), however, the carpels are more or less grown together; and in the cherry, peach, etc., there is but a single carpel giving rise to a single-seeded stone-fruit (drupe) (Fig. 114, _E_, _H_). In the strawberry (Fig. 114, _A_), rose (_G_), cinquefoil (_Potentilla_), etc., there are numerous distinct, one-seeded carpels, and in _Spiraea_ (Fig. 114, _F_) there are five several-seeded carpels, forming as many dry pods when ripe. The so-called "berry" of the strawberry is really the much enlarged flower axis, or "receptacle,"

in which the little one-seeded fruits are embedded, the latter being what are ordinarily called the seeds.

[Ill.u.s.tration: FIG. 114.--_Calyciflorae_ (_Rosiflorae_). _A_, inflorescence of strawberry (_Fragaria_), . _B_, a single flower, 1. _C_, section of _B_. _D_, floral diagram. _E_, vertical section of a cherry-flower (_Prunus_), 1. _F_, vertical section of the flower of _Spiraea_, 2. _G_, vertical section of the bud of a wild rose (_Rosa_), 1. _H_, vertical section of the young fruit, 1.

_I_, section of the flower of an apple (_Pyrus_), 1. _J_, floral diagram of apple.]

From the examples given, it will be seen that the order includes not only some of the most ornamental, cultivated plants, but the majority of our best fruits. In addition to those already given, may be mentioned the raspberry, blackberry, quince, plum, and apricot.

[Ill.u.s.tration: FIG. 115.--_Calyciflorae_ (_Leguminosae_). _A_, flowers and leaf of the common pea, _Pisum_ (_Papilionaceae_), . _t_, tendril. _st._ stipules. _B_, the petals, separated and displayed, 1. _C_, flower, with the calyx and corolla removed, 1. _D_, a fruit divided lengthwise, . _E_, the embryo, with one of the cotyledons removed, 2. _F_, diagram of the flower. _G_, flower of red-bud, _Cercis_ (_Caesalpinaceae_), 2. _H_, the same, with calyx and corolla removed. _I_, inflorescence of the sensitive-brier, _Schrankia_ (_Mimosaceae_), 1. _J_, a single flower, 2.]

The last order of the _Calyciflorae_ and the highest of the _Choripetalae_ is the order _Leguminosae_, of which the bean, pea, clover, and many other common plants are examples. In most of our common forms the flowers are peculiar in shape, one of the petals being larger than the others, and covering them in the bud. This petal is known as the standard. The two lateral petals are known as the wings, and the two lower and inner are generally grown together forming what is called the "keel" (Fig. 115, _A_, _B_). The stamens, ten in number, are sometimes all grown together into a tube, but generally the upper one is free from the others (Fig. 115, _C_). There is but one carpel which forms a pod with two valves when ripe (Fig. 115, _D_). The seeds are large, and the embryo fills the seed completely. From the peculiar form of the flower, they are known as _Papilionaceae_ (_papilio_, a b.u.t.terfly). Many of the _Papilionaceae_ are climbers, either having twining stems, as in the common beans, or else with part of the leaf changed into a tendril as in the pea (Fig. 115, _A_), vetch, etc. The leaves are usually compound.

Of the second family (_Caesalpineae_), mainly tropical, the honey locust (_Gleditschia_) and red-bud (_Cercis_) (Fig. 115, _G_) are the commonest examples. The flowers differ mainly from the _Papilionaceae_ in being less perfectly papilionaceous, and the stamens are almost entirely distinct (Fig. 115, _H_). The last family (_Mimosaceae_) is also mainly tropical. The acacias, sensitive-plant (_Mimosa_), and the sensitive-brier of the southern United States (_Schrankia_) (Fig. 115, _I_) represent this family. The flowers are quite different from the others of the order, being tubular and the petals united, thus resembling the flowers of the _Sympetalae_. The leaves of _Mimosa_ and _Schrankia_ are extraordinarily sensitive, folding up if irritated.

CHAPTER XIX.

CLa.s.sIFICATION OF DICOTYLEDONS (_Continued_).

DIVISION II.--_Sympetalae_.

The _Sympetalae_ or _Gamopetalae_ are at once distinguished from the _Choripetalae_ by having the petals more or less united, so that the corolla is to some extent tubular. In the last order of the _Choripetalae_ we found a few examples (_Mimosaceae_) where the same thing is true, and these form a transition from the _Choripetalae_ to the _Sympetalae_.

There are two great divisions, _Isocarpae_ and _Anisocarpae_. In the first the carpels are of the same number as the petals and sepals; in the second fewer. In both cases the carpels are completely united, forming a single, compound pistil. In the _Isocarpae_ there are usually twice as many stamens as petals, occasionally the same number.

There are three orders of the _Isocarpae_, viz., _Bicornes_, _Primulinae_, and _Diospyrinae_. The first is a large order with six families, including many very beautiful plants, and a few of some economic value. Of the six families, all but one (_Epacrideae_) are represented in the United States. Of these the _Pyrolaceae_ includes the pretty little pyrolas and prince's-pine (_Chimaphila_) (Fig. 116, _J_); the _Monotropeae_ has as its commonest examples, the curious Indian-pipe (_Monotropa uniflora_), and pine-sap (_M. hypopitys_) (Fig. 116, _L_). These grow on decaying vegetable matter, and are quite devoid of chlorophyll, the former species being pure white throughout (hence a popular name, "ghost flower"); the latter is yellowish. The magnificent rhododendrons and azaleas (Fig. 116, _F_), and the mountain laurel (_Kalmia_) (Fig. 116, _I_), belong to the _Rhodoraceae_. The heath family (_Ericaceae_), besides the true heaths (_Erica_, _Calluna_), includes the pretty trailing-arbutus or may-flower (_Epigaea_), _Andromeda_, _Oxydendrum_ (Fig. 116, _E_), wintergreen (_Gaultheria_), etc. The last family is represented by the cranberry (_Vaccinium_) and huckleberry (_Gaylussacia_).

[Ill.u.s.tration: FIG. 116.--Types of _Isocarpous sympetalae_ (_Bicornes_). _A_, flowers, fruit, and leaves of huckleberry, _Gaylussacia_ (_Vaccinieae_), 1. _B_, vertical section of the flower, 3. _C_, a stamen: i, from in front; ii, from the side, 4. _D_, cross-section of the young fruit, 2. _E_, flower of sorrel-tree, _Oxydendrum_ (_Ericaceae_), 2. _F_, flower of azalea (_Rhododendron_), . _G_, cross-section of the ovary, 3. _H_, diagram of the flower.

_I_, flower of mountain laurel (_Kalmia_), 1. _J_, prince's-pine, _Chimaphila_ (_Pyrolaceae_), . _K_, a single flower, 1. _L_, plant of pine-sap, _Monotropa_, (_Monotropeae_), . _M_, section of a flower, 1.]

The second order, the primroses (_Primulinae_), is princ.i.p.ally represented in the cooler parts of the world by the true primrose family (_Primulaceae_), of which several familiar plants may be mentioned. The genus _Primula_ includes the European primrose and cowslip, as well as two or three small American species, and the commonly cultivated Chinese primrose. Other genera are _Dodecatheon_, of which the beautiful shooting-star (_D. Meadia_) (Fig. 117, _A_) is the best known. Something like this is _Cyclamen_, sometimes cultivated as a house plant. The moneywort (_Lysimachia nummularia_) (Fig. 117, _D_), as well as other species, also belongs here.

[Ill.u.s.tration: FIG. 117.--_Isocarpous sympetalae_ (_Primulinae_, _Diospyrinae_). _A_, shooting-star, _Dodecatheon_ (_Primulaceae_), .

_B_, section of a flower, 1. _C_, diagram of the flower. _D_, Moneywort, _Lysimachia_ (_Primulaceae_), . _E_, a perfect flower of the persimmon, _Diospyros_ (_Ebenaceae_), 1. _F_, the same, laid open: section of the young fruit, 2. _H_, longitudinal section of a ripe seed, 1. _em._ the embryo. _I_, fruit, .]

The sea-rosemary (_Statice_) and one or two cultivated species of plumbago are the only members of the plumbago family (_Plumbagineae_) likely to be met with. The remaining families of the _Primulinae_ are not represented by any common plants.

The third and last order of the _Isocarpous sympetalae_ has but a single common representative in the United States; viz., the persimmon (_Diospyros_) (Fig. 117, _E_). This belongs to the family _Ebenaceae_, to which also belongs the ebony a member of the same genus as the persimmon, and found in Africa and Asia.

The second division of the _Sympetalae_ (the _Anisocarpae_) has usually but two or three carpels, never as many as the petals. The stamens are also never more than five, and very often one or more are abortive.

[Ill.u.s.tration: FIG. 118.--Types of _Anisocarpous sympetalae_ (_Tubiflorae_). _A_, flower and leaves of wild phlox (_Polemoniaceae_), . _B_, section of a flower, 1. _C_, fruit, 1. _D_, flower of blue valerian (_Polemonium_), 1. _E_, flowers and leaf of water-leaf, _Hydrophyllum_ (_Hydrophyllaceae_), . _F_, section of a flower, 1. _G_, flower of wild morning-glory, _Convolvulus_ (_Convolvulaceae_), . One of the bracts surrounding the calyx and part of the corolla are cut away. _H_, diagram of the flower. _I_, the fruit of a garden morning-glory, from which the outer wall has fallen, leaving only the inner membranous part.i.tions, 1. _J_, a seed, 1.

_K_, cross-section of a nearly ripe seed, showing the crumpled embryo, 2. _L_, an embryo removed from a nearly ripe seed, and spread out; one of the cotyledons has been partially removed, 1.]

The first order (_Tubiflorae_) has, as the name indicates, tubular flowers which show usually perfect, radial symmetry (_Actinomorphism_).

There are five families, all represented by familiar plants. The first (_Convolvulaceae_) has as its type the morning-glory (_Convolvulus_) (Fig. 118, _G_), and the nearly related _Ipomas_ of the gardens. The curious dodder (_Cuscuta_), whose leafless, yellow stems are sometimes very conspicuous, twining over various plants, is a member of this family which has lost its chlorophyll through parasitic habits. The sweet potato (_Batatas_) is also a member of the morning-glory family.

The numerous species, wild and cultivated, of phlox (Fig. 118, _A_), and the blue valerian (_Polemonium_) (Fig. 118, _D_), are examples of the family _Polemoniaceae_.

[Ill.u.s.tration: FIG. 119.--_Anisocarpous sympetalae_ (_Tubiflorae_). _A_, inflorescence of hound's-tongue, _Cynoglossum_ (_Borragineae_), .

_B_, section of a flower, 2. _C_, nearly ripe fruit, 1. _D_, flowering branch of nightshade, _Solanum_ (_Solaneae_), . _E_, a single flower, 1. _F_, section of the flower, 2. _G_, young fruit, 1. _H_, flower of _Petunia_ (_Solaneae_), . _I_, diagram of the flower.]

The third family (_Hydrophyllaceae_) includes several species of water-leaf (_Hydrophyllum_) (Fig. 118, _E_) and _Phacelia_, among our wild flowers, and species of _Nemophila_, _Whitlavia_ and others from the western states, but now common in gardens.

The Borage family (_Borragineae_) includes the forget-me-not (_Myosotis_) and a few pretty wild flowers, _e.g._ the orange-flowered pucc.o.o.ns (_Lithospermum_); but it also embraces a number of the most troublesome weeds, among which are the hound's-tongue (_Cynoglossum_) (Fig. 119, _A_), and the "beggar's-ticks" (_Echinospermum_), whose p.r.i.c.kly fruits (Fig. 119, _C_) become detached on the slightest provocation, and adhere to whatever they touch with great tenacity.

The flowers in this family are arranged in one-sided inflorescences which are coiled up at first and straighten as the flowers expand.

The last family (_Solaneae_) includes the nightshades (_Solanum_) (Fig. 119, _D_), to which genus the potato (_S. tuberosum_) and the egg-plant (_S. Melongena_) also belong. Many of the family contain a poisonous principle, _e.g._ the deadly nightshade (_Atropa_), tobacco (_Nicotiana_), stramonium (_Datura_), and others. Of the cultivated plants, besides those already mentioned, the tomato (_Lycopersic.u.m_), and various species of _Petunia_ (Fig. 119, _H_), _Solanum_, and _Datura_ are the commonest.

The second order of the _Anisocarpae_ consists of plants whose flowers usually exhibit very marked, bilateral symmetry (_Zygomorphism_). From the flower often being two-lipped (see Fig. 120), the name of the order (_l.a.b.i.atiflorae_) is derived.

Of the nine families const.i.tuting the order, all but one are represented within our limits, but the great majority belong to two families, the mints (_l.a.b.i.atae_) and the figworts (_Scrophularineae_).

The mints are very common and easily recognizable on account of their square stems, opposite leaves, strongly bil.a.b.i.ate flowers, and the ovary splitting into four seed-like fruits (Fig. 120, _D_, _F_).