SPECIES OP CASSIA WHICH YIELD SENNA. 
181 
the memoir of M. Nectoux were led to the same opinion, 
and reported accordingly. There is a passage in this memoir 
which implies a knowledge of contemporaneous publications 
and even evinces a little feeling of jealousy on the part of the 
writer; he there states "that he can affirm that he is the only 
one who has verified upon the spot, the principal facts pre- 
sented in this memoir, though he may not have been the first 
to bring them before the Institute." 
The two descriptions given above are at issue as regards the 
existence of glands upon the petiole, and also as to the idea 
intended to be given of the form of the leaflets. Now, the 
question arises, admitting the same species to have been 
seen by both observers, are the characters specified so change- 
able as to allow an explanation founded upon the variable na- 
ture of which all plants, more or less, partake? It is well known 
that in comparing a long series of specimens appertaining to 
a single species, they may be so arranged that an individual 
specimen, at one end of the series, may be so widely different 
from another, at the other end, as to lead to the impression 
that they are distinct, but yet, by progressing through each 
link of the chain of analogies, the resemblance between conti- 
guous specimens is so close as to preclude the possibility of 
separating them, and therefore the identity of the whole must 
be maintained. Great disparity also arises from the condition 
of advancement at which plants are observed; as also, from 
the nature of the soil, exposure to light, heat and other 
physical circumstances incident to the locality in which they 
grow. The demand for Senna in Europe, according to the 
confession of the native agents, having charge of the depots, 
is greater than the supply of such as is considered of the best 
quality, which is cultivated in the country of the Barabras; 
hence it became the practice to make up the deficiency by 
introducing that which in the neighbourhood of the depots 
most remote from Cairo, is called "wild" (sauvage) or unculti- 
vated; this fact is of vast importance in estimating the causes 
of variety. — These considerations must have decided influ- 
ence in explaining the want of uniformity, and proneness to 
