JOURNAL OF PROCEEDINGS. 
167 
M. pusilla , it is 2-4 times as large as the seed. In thejarge edible fruits of 
Cereij such as C. triangularis, C. grandtjlorus, C. gtganteus, etc., it consti¬ 
tutes by far the largest part of the fruit. The cells are globular, oval, or 
variously compressed ; in some species I find them extremely small, 0.01- 
0.03 1. long, while in others they are 0.1-0.2 and even 0.3 1. long. 
The genus Opuntia apparently differs in having the whole seed covered 
with juicy cells, which, in size and quantity, vastly predominate over the 
cells of the rather insignificant funiculus proper. But the whole bony 
coating of the seed being but an arillary enlargement of the funiculus, 
(Cact. Mex. Bound., p. 76,) this peculiar case entirely falls into the 
analogy of the other Cactacea. The real difference is caused by the 
nature of the arillus, which, getting extremely hard, leaves the cells of 
the epidermis only to grow out, and finally to form the pulp of the fruit. 
Soon after fecundation these cells gradually become elongated, cylindrical, 
and disconnected among one another, rising perpendicularly from the 
surface of the seed; they are shorter, of nearly equal length, and per¬ 
fectly straight, on the faces of the young seed, and longer, hair-like, 
and twisting in different directions on and near "the rim. In O. glau - 
cophylla, which I take to be a mere variety of O. Ficus Indica , I find 
them at their first appearance on a seed of less than one line in di¬ 
ameter only about 0.004 1. long and wide; on the rim they soon grow 
to twice the diameter and ten times the length, till at maturity the larger 
ones are 0.3-0.5 1. long. These cells, at first simple and cylindrical, 
become at last jointed and clavate, the terminal cells being many times 
larger than the basal ones, thus properly filling the interstices between 
the seeds. During winter, the fruit and seeds having reached their full 
growth, these cells contain a colorless, viscous, insipid fluid ; in the 
following spring, when the fruit has assumed a deep purple colour, and 
attained full maturity, they contain a sweetish, purple liquid, and 
soon separate, forming what is properly called the pulp. The single 
cells are mostly oval or oblong, 0.02-0.20 1. in length. I find the same 
structure in O. Engelmanni, which, however, ripens its fruit, with us, 
in autumn, and it undoubtedly obtains in all Opuntiae with large and 
juicy fruit. 
In O. Rafinesquii, and probably in all species with less juicy fruit, the 
cells on the face of the seed are not developed, only those on the rim 
producing the pulp, which in this species as well as in O. vulgaris and 
O. Pes Corvi, remains, even at full maturity, insipid and viscous and of 
pale red colour. In this condition the fruit adheres to the plant, without 
any change, until it falls off in the following spring. 
In O. Brasiliensis and O. monacantha these epidermis-cells are greatly 
elongated, forming, in fact, a matted, tough beard, 2-3 lines long, analo¬ 
gous to that of the unripe cottonseed; each hair consists of several 
slender joints, 0.01-0.02 1. in diameter, the terminal one often thickly cla¬ 
vate or otherwise variously inflated. I have found them thus in the 
unripe fruit late in autumn ; how they may change at maturity I have 
been unable to ascertain. 
No such development of the epidermis-cells seems to take place in the 
Opuntiae with dry fruit, such as O. Missouriensis, O. clavata, etc. ; the 
seed, consequently, has a whiter, polished, ivory-like surface, while that 
of the juicy Opuntiae fruits is dull and almost rough, and not so white. 
The cells of the parenchyma of the fruit, as well as those of the bony 
seed-coat, are full of aggregations of crystals ; those of the funiculus 
proper contain fewer and smaller clusters ; but in the pulp itself I have 
never seen them; neither could Tdiscover any in the parenchyma, or in 
the pulp of the fruits of Mamillariae. 
Dr. J. S. Newberry, of Cleveland, O., and Prof. Chas. T. 
Jackson, of Boston, Mass., were elected Corresponding Mem¬ 
bers. 
