STEMS, LEAVES, AND BUDS. 
41 
the incrustation, that they are derived from the original mem- 
brane of the cell. Tincture of iodine renders the membrane 
opaque, which evidently shows, that the interstices have no 
openings. The bands are evidently the result of a partial 
conversion into wood, and, indeed, no better instance can be 
given, to illustrate and confirm the correctness of the view 
which Schleiden has given of the origin of the bands and 
fibres in the vessels and cells, than the Cycas revoluta. The 
author being anxious to ascertain whether the bands already 
existed at a former period, examined a young undeveloped 
frond, about two weeks old, and was glad to find his opinion 
confirmed ; the cells were of a uniform transparency, and 
exhibited neither dots nor bands, but had a distinct cytoblast 
or nucleus, which had entirely disappeared from those cells in 
which the incrusting material was observed ; which proves, that 
this incrusting material had formed itself at the expense of 
the nucleus. The material which forms the band is connected, 
and has evidently not been produced by a growing together, 
as one might suppose, for it is perfectly solid, and exhibits no 
disposition to unroll itself, or to degenerate into fibres. The 
bands were probably produced by the circumstance, that the 
incrusting substance, which first flowed over the walls in a 
liquid state, contracted itself, and by the mere efiect of 
condensation, supported by the distention, and probably the 
enlargement of the cells, naturally left parts of the primitive 
membrane uncovered. The author, however, notwithstanding 
the analogies exhibited by the reproductive organs, considers 
the relationship between the Cycadem and the Coniferce very 
remote, and supposes the Cycadem to be the remnants of a 
class of plants which belonged to a former vegetation. 
The description is accurate and striking, and his conclu- 
sion, that the Cycadem has but a remote relationship with the 
Coniferm, ought to be well considered by those who assimilate 
these two natural orders with each other. A similar analogy 
takes place among the Orchidem and the Asclepiadem with 
regard to the fructification, and yet no one will be bold enough 
to place them under one head in the natural system. 
The approbation which the author gives to Schleiden is 
433 2 E 
