396 Observations and Experiments on some Plants 



which, perhaps, possesses the quality in question in a greater 

 decree than any other. I had thus an opportunity of making 

 observations and trying experiments, the result of which I shall 

 proceed to state, first giving a short description of the general 

 habits of the arachis, which will facilitate the comprehension of 

 the subject. 



The ^'rachis hypogse^a, or earth nut {Jig. 62.), is one of the 

 Leguminaceae. It was brought to 

 England in 1712, and it is here con- 

 sidered a stove plant. It is generally 

 cultivated in the warmer parts of 

 North and South America, but is 

 supposed to be originally from Africa. 

 In South Carolina, the seeds are used 

 as chocolate; in the eastern countries, 

 as almonds ; and in Cochin-China 



they furnish an oil used for lamps, and as a substitute for the oil 

 of olives. About Paris, it is raised on hot-beds, and trans- 

 planted into the open garden, where it ripens its seeds, which are 

 used as other legumes. It has also been brought to maturity in 

 a stove in England, and proved very prolific. (See Hort. Trans., 

 vol. V. p. 372.) 



The greater number of the flowers of the arachis originate 

 in that portion of the stem which is nearest to the surface of the 

 soil ; some, however, are to be found a little higher up, in the 

 axils of the leaves. The calyx of these flowers forms a tube at 

 the lower end, which resembles a peduncle. The style is enclosed 

 in it, and it terminates in a little ovary, at first sessile, and placed 

 at the base of the tube. After being fecundated, the flower 

 withers and falls off*, and a small tubercle is found adhering to 

 the stem, which, by degrees, assumes a longer shape, like that of 

 a little horn, and, turning downwards, penetrates into the soil, 

 or sinks deeper, if it has already entered it. This little horn 

 (which is nothing more than the fecundated seed attached to a 

 peduncle) increases in the earth, becoming larger towards its 

 point, till, by degrees, it assumes the appearance of the legume, 

 or seed-pod, of the arachis. 



From knowing that, in general, the parts of plants which are 

 under the soil are either roots themselves, or are furnished with 

 fibrils, and that they can only derive nourishment from the soil 

 by their spongioles, the idea struck me, that the fruit of the ara- 

 chis might have an analogy with roots, or might exercise a simi- 

 lar function in some degree : and I very soon, by observing the 

 plant attentively, discovered, even with the naked eye, a small 

 tubercle on the extreme point of each legume, which, on ex- 

 amining it with a glass, and afterwards with a microscope, I 

 found to be analogous with, though it was much more distinct 



