373 
and some other families ; Nees v. Esenbeck, on the contrary, seems to enter- 
tain the opinion that this cotyledon is a special organ, for which he retains 
Richard’s name of hypoblastus, although he does not adopt the view that bo- 
tanist took of its nature. But I think if w’e consider the improbability of any 
special organ being provided for Grasses, which is not found elsewhere, and if 
we consider how nearly alike are the embryos of Grasses and certain Aracese, 
in which the plumule lies within a cleft of the cotyledon, it is impossible to 
doubt the identity of the hypoblastus of Richard and Nees v. Esenbeck, and 
the cotyledon of other Monocotyledons. Indeed, the latter himself appears, 
in one place, to hesitate about the accuracy of distinguishing them, when he 
says (p. 9), “ Turn vero hypoblastus pars quaedam habenda est cotyledon! 
analoga, magisque ad inter! ora seminis quam ad externam corculi evolutionem 
spectans.” 
The structure of the stem of Grasses is so much at variance, apparently, 
with that of other Endogenous plants, as to have led Agardh to remark, that 
it is the least monocotyledonous of all Monocotyledonous plants. It is pro- 
bable, however, that its pecuharity does not depend so much upon any 
specific deviation from the ordinary laws of growth in Endogens, as upon a 
separation of the parts at an early period of their growth. The stem of a 
Grass, it must be remembered, exists in two different states, — that of the 
rhizoma, and of the culm : the rhizoma, which is the true trunk ; and the 
culm, which may be considered a ramification of it. The rhizoma grows 
slowly, and differs in no respect from the stem of other Monocotyledons, as 
is evident in that of the Bamboo. The culm, on the contrary, which grows 
with great rapidity, is fistular, with a compact impervious diaphragm at each 
articulation ; a fact which must be familiar to every one who has examined 
a straw, or the joint of a Bamboo. In the beginning, when this culm was first 
developed, it was a solid body like the rhizoma, only infinitely smaller ; but in 
consequence of the great rapidity of its developement,. the cellular tissue forms 
more slowly that the woody vascular bundles which it connects, and in con- 
sequence a separation takes place between the latter and the former, ex- 
cept at the articulations, where, by the action of the leaves and their axil- 
lary bnds, is formed a plexus of vessels, which grows as rapidly as the culm 
distends, and therefore never separates in the centre. Something analogous 
to this occurs in the fiowering stem of the common Onion among Monocotyle- 
dons, and in Umbelliferse among Dicotyledons. 
The strict relation that exists between Palms and Grasses has been already 
adverted to in speaking of the foraier order : hence Nees v. Esenbeck con- 
siders Grasses to be a sort of Palms of a lower grade. In reality, the habit of 
the genera Cadamus and Bambusa is nearly alike ; the inflorescence of Grasses 
may be considered to be the same as that of Palms, the floral envelopes of the 
latter taken away, and only their bracts remaining ; and, finally, their leaves 
are formed upon exactly the same plan, with this difference only, that those of 
Grasses are undivided. With Cyperaceae, however, it is that Grasses are most 
properly to be compared : while a manifest tendency, at least to the degree of 
verticillation requisite to constitute a calyx, evidently takes place in the paleae 
of Grasses, Cyperacese are destitute of aU trace of such a tendency, unless the 
opposite connate glumes of the female flowers of Carex, or the h\q)Ogynous 
scales of certain Schoeni and others, be considered an approach to the pro- 
duction of a perianth. For this reason. Grasses are to be considered plants 
in a higher state of evolution than Cyperaceae. Independently of this differ- 
ence, the orders are readily known by the stems of Grasses being round, those 
of Cyperaceae angular ; the leaves of Grasses having a hgula at the apex 
of their sheath, which is split, while the sheath of Cyperaceae is not split, and 
