Illustrations of Indian Botany, Vol. 1/Cruciferae
The large assemblage of plants ranged under this order, forming one of the most natural families of the vegetable kingdom, have but few representatives within the tropics : scarcely 20 indigenous species, out of upwards of 1000 belonging to the order, being found within the tropical regions of India ; and even these, being principally confined to alpine districts. The plants composing this order are for the most part herbaceous, rarely suffruticose, with watery- juices; and round, or irregularly angled, stems. The leaves are simple and entire, or variously divided, rarely truly compound. The flowers hermaphrodite, regular, racemose, or rarely Solitary and axillary. Sepals 4, deciduous, cruciate, the lateral ones gibbous, or spurred at the base. Corolla hypogynous, cruciform, petals 4, alternate with the sepals, deciduous, stamens 6, the two, opposite the lateral sepals, shorter, and occasionally toothed, 4, in pairs, opposite the anterior and posterior sepals, longer : anthers bilocular, introrse. Torus with several glands between the petals and the stamens, and the ovarium. Ovary usually bilocular with parietal placentas, generally, meeting in the middle, and forming a spurious partition, stigmas two opposite the placentas. Fruit a siliqua orsilicule, rarely one-celled and indehiscent, usually opening by two valves separating from the placentae. Seeds attached in a single row, by a funiculus, to each side of the placentas, generally pendulous. Albumen none, embryo with the radical folded up on the cotyledons : if on the edge they are said to be accumbent, if on the back incumbent, sometimes the cotyledons are folded, they are then said to be conduplicate incumbent, &c. (In Nasturtium they are accumbent, in Lepidium incumbent, the cotyledons in the latter 3-lobed.)
Affinities. The nearest affinities of this order are with Capparidere, agreeing in the quaternary number of the divisions of the flower : in the fruit having two placentae, and a similar mode of dehiscence ; and in the stamens of some species of the Capparidece, agreeing in number. They have also some affinities with Fumariacece as already shewn under that order, but are kept distinct by the different structure of the seed.
Essential Character. Flowers polypetalous, stamens tetradynamous. Ovary wholly superior, the carpels combined into a solitary pistillum : seeds without albumen. Leaves alternate, destitute of stipules.
Geographical Distribution. I have remarked above that the species of this order are very rare within the tropics. Europe indeed maybe esteemed the head quarters of Cruciferce $ but they are abundant all over the temperate zone of the northern hemisphere, and comparatively rare in the southern : upwards of 600 appertaining to the one, and scarcely 100 to the other. But to enter into minute details of the geographical distribution of an almost extra Indian order in a work on Indian Botany, can be of but little avail ; I may however observe, that many are cultivated both for use and ornament in this country, and it seems not improbable, that the number might be increased, at least during the cool season, owing to most of them being annual, and requiring in this country but a few months to attain maturity. Whether attemps for their naturalization will ever so far succeed on the plains as to render us independent of more temperate climates for our supplies of seed, is a question still to be solved, but one, the solution which, when we consider their value to mankind, ought not to be readily relinquished, even though the chances against success, appear to preponderate. If this desirable object is ever to be accomplished, it must undoubtedly be through gradual extension from the more elevated and cooler regions, to the lower and warmer ones. One source of disappointment, viz. the oily nature of their seed, is not easily guarded against, as oily seeds generally soon deteriorate, and I presume more rapidly in a warm climate : while, owing to the long interval that intervenes between their arrival at maturity, and the period for sowing, they are exposed so much the more to this source of deterioration.
Properties and Uses. Acrimony, more or less combined with bitterness, forms the predominant quality of the Cruciferce, in proof of which it is only necessary to mention, Horse-radish, Mustard, Cress, the common Radish, and Water-cress, all of which possess this property in an eminent degree, and even the cabbage, now so much used when ameliorated by cultivation, as aliment, possesses in its wild state much of the acrid properties inherent in the family. The principle on which their acrimony depends is of a volatile nature, and is greally diminished by drying. Formerly it was attributed to the presence of volatile alkali, but carefulchemical analysis proved the erroneousness of this opinion, by showing the total absence of ammonia, in the recent state of these plants, or in, their expressed juices, though, during the process of putrefaction, it is exhaled in considerable quantity : hence it must be generated during decomposition, and is attributable to nitrogen, which enters largely into their composition. The more prevalent opinion now is, that their acrimony owes its existence to the presence of volatile oil, an opinion resting on a better foundation, though reasoning from analogy, I strongly suspect not without some exceptions, as we do not in all the instances cited, find it combined with aromatic properties, any more than in Ranunculacece . It is said however, to exist not only in all the Cruciferce, but in all parts of these vegetables, varying only in intensity. To this active, but very volatile principle, of whatever nature it be, they owe their medicinal virtues, which are stimulant and antiscorbutic, but which, requires, them to be used fresh, since it is lost by drying. The seed fortunately retain their properties for a greater length of time, and those of white mustard have been long celebrated for their tonic and stomatic virtues. The Tamul doctors attribute similar virtues to their Aliverie or Saliverie, the Arabis chinensis of Rottler and Ainslie, but which, I have ascertained to be merely the English Garden cress, Lepidium sativum, as may be seen from the accompanying plate, taken from a specimen raised in my garden from bazar seed.
Our cabbages, turnips, radishes, knolkoles, &c. which belong to this family, are all too well known to require notice here; they owe their fitness for food to their acrid properties being diluted by an abundance of mucilage. Several species, such as the rape and mustard, are cultivated in Europe on account of the oil which their seeds contain, but could never be profitably raised in this country for that purpose.
Under this head I shall only further observe, that one of the species here figured, which is not a native, was introduced for the purpose of determining to what genus, the so-called Aliverie actually belonged, and to assign to the proper plant, the merit which is its due. The other figure was made from a native specimen. Two species of the genus Cardamine are found truly native on both the Neilgherries and Pulney mountains, the Capsella (Sheepherd purse) is also found in abundance on the former of these ranges, but I suspect introduced with corn seed.
EXPLANATION OF PLATES 12 and 13.
12.—1. Plant of Lepidium Sativum — natural size. 2. Flower opened, to show the calyx, petals, stamens, and ovary. 3. Portion of a racime, with fruit. 4. Capsule before dehiscence. 5. The same burst, showing the seed in situ. 6. A seed cut transversely, showing the radical incumbent on the three 3-lobed cotyledons. 7. A seed cut longitudinally, showing the situation of the radical and cotyledons. 8 and 9. Different views of the radical and cotyledons removed from the testa, and partially opened out — all more or less magnified. 13.—1. Plant of Nasturtium Madagascariense—natural size. 2. Flower opened to show the different parts. 3. The same, sepals and petals removed. 4. Stamens back and front view. 5. Capsule. 6. The same cut transversely. 7. Placenta? after the valves of the Capsule have separated, showing the position of the seeds. 8. A seed. 9. The same cut transversely, showing the accumbent radical. 10. Embryo removed from the testa, showing the cotyledons and radical — all more or less magnified.