VEGETABLE AND ANIMAL LIFE. 



99 



flourish entirely covered with water, or with their roots alone shooting into 

 a moist soil. 



Animals of various kinds are aerial : perhaps the term is not used with 

 strict correctness. It will, at least, apply with more correctness to plants. 

 All the most succulent plants of hot climates are of this description: such are 

 several of the palms and of the canes ; and the greater number of plants that 

 embellish the arid Karro fields of the Cape of Good Hope.* Succulent as 

 they are, these will only grow in soils or sands so sere and adust that no 

 moisture can be extracted from them, and are even destroyed by a full supply 

 of wet or by a rainy season. The SoldLudrd. grandi/lora, a Jamaica shrub, was 

 long propagated in our own stoves by cuttings, which, though freely watered, 

 could never be made to produce any signs of fructification, notwithstanding 

 that the cuttings grew several feet in length every season. By accident a 

 pot with young cuttings was mislaid and forgotten in the Kew garden, and 

 had no water given it; it was hereby reduced to its healthy aridity, and every 

 extremity produced a flower.f 



And hence it is an opinion common to many of the ablest physiologists of 

 the present day, that these derive the whole of their nutriment from the sur- 

 rounding atmosphere ; and that the only advantage which they acquire from 

 thrusting their roots into such strata is that of obtaining an erect position. 

 There are some quadrupeds that appear to derive nutriment in the same man- 

 ner. Thus the bradypus tridactylus, or sloth, never drinks, imbibes by its 

 cutaneous absorbents, and trembles at the feeling of rain ; and, in common 

 with the bird tribes, has only one ultimate or excrementary duct; while the 

 olive cavy| avoids water of every kind almost as pertinaciously as does also 

 the ostrich, which is in consequence said by the Arabs never to drink. And 

 yet these are animals almost as succulent as any we are acquainted with. 



But, however true this may be with regard to animals, we have manifest 

 proofs that vegetables of certain tribes and descriptions are altogether sup- 

 ported by the atmosphere that surrounds them ; for, important as is the organ 

 of a root to plants in general, there are several which have no root whatever, 

 and can derive nutriment in no other way. The water-caltrop^ is an instance 

 directly in point. The seed of this plant has no rostel, and consequently can 

 never, in the first instance, become rooted. From the horned nut or pericarp 

 of the seed, as it lies in water, which is its natural element, shoots forth a 

 long plumule perpendicularly towards the surface of the stream ; during the 

 ascent of which a variety of capillary branched leaves shoot forth from the 

 sides of the plumule, some of which bend downward, and fix the whole plant 

 to the bottom by penetrating into the soil below the stream ; the leaves alone 

 in this late stage of germination acting the part of a root, and giving maturity 

 to the still unfinished plant. The cactus genus, in some of its very numerous 

 species, offers us an example of similar evolution ; and especially in the 

 opuntia tribe, or that which embraces the prickly pears or Indian figs of our 

 green-houses, of Mdiich the cochineal plant|| is one form. Of these, several 

 grow by the mere introduction of one of their thick fleshy leaves into a soil 

 of almost any kind that is sufficiently dry; they obtain an erect position, but 

 never root, or shoot forth radicles : and hence almost the whole of their 

 moisture must necessarily be derived from the surrounding atmosphere. 



Perhaps one-half of the fuci have no root whatever : many of them, indeed, 

 consist of vesicles or vesicular bulbs alone, sessile upon the matrix of some 

 stone or shell that supports them, and propagate their kinds by offsets, with- 

 out any other vegetable organs. The seeds of the fucus prolifer sometimes 

 evolve nothing but a leaf; the plant being propagated also by leaf upon leaf, 

 either forked or elliptic, without root. 



The aphyteia hydnora is a curious instance in point. This plant is equally 

 destitute of leaves, stem, and root ; and consists alone of a sessile, coriaceous, 



* The only rain that waters this tract is that which falls for a few weeks in the winter : during the hot 

 and fertile months there is no rain whatever. t Smith's Introduction to TJotany, &c. p. 141. 



t Cavia aciiscky. This is the more extraordinary, because the C. cobaya, or guinea-pig, drinks freely, 

 and the C. capybara, or river cavy, is fond of swimming and diving. 



$ Trapa nutans. \\ Cactus coccinellifcr. 



G 2 



