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appears to be greater in the exterior or lower valve ; so that a gluma consist- 
ing of one valve may, in all cases, be considered as deprived of its outer or 
inferior valve. In certain genera with a simple spike, as Lolium and Lep- 
turus, this is clearly proved by the structure of the terminal flower or spicula, 
which retains the natural number of parts ; and in other genera not admitting 
of this direct proof, the fact is established by a series of species shewing its 
gradual obliteration, as in those species of Panicum which connect that genus 
with Paspalum. On the other hand, in the inner envelope, or calyx of Jus- 
sieu, obliteration first takes place in the inner or upper valve ; but this valve 
having, instead of one central nerve, two nerves equidistant from its axis, I 
consider it as composed of two confluent valves, analogous to what takes 
place in the calyx and corolla of many irregular flowers of other classes ; and 
this confluence may be regarded as the first step towards its obliteration, 
which is complete in many species of Panicum, in Andropogon, Pappopho- 
rum, Alopecurus, Trichodium, and several other genera. With respect to 
the nature of this inner or proper envelope of Grasses, it may be observed, 
that the view of its structure now given, in reducing its parts to the usual 
ternary division of Monocotyledones, aflbrds an additional argument for con- 
sidering it as the real perianthium. This argument, however, is not conclu- 
sive, for a similar confluence takes place between the two inner lateral bractese 
of the greater part of Iridese ; and with these, in the relative insertion of its 
valves, the proper envelope of Grasses may be supposed much better to 
accord than with a genuine perianthium. If, therefore, this inner envelope 
of Grasses be regarded as consisting merely of bracteae, the real perianthium 
of the order must be looked for in those minute scales, which, in the greater 
part of its genera are found immediately surrounding the sexual organs. 
These scales are, in most cases, only two in number, and placed collaterally 
within the inferior valve of the proper envelope. In their real insertion, 
however, they alternate with the valves of this envelope, as is obviously the 
case in Ehrharta and certain other genera ; and their collateral approxima- 
tion may be considered as a tendency to that confluence which uniformly 
exists in the parts composing the upper valve of the proper envelope, and 
which takes place also between these two squamae themselves, in some 
genera, as Glyceria and Melica. In certain other genera, as Bambusa and 
Stipa, a third squamula exists, which is placed opposite to the axis of the 
upper valve of the proper envelope, or, to speak in conformity with the view 
already taken of the structure of this valve, opposite to the junction of its 
two component parts. With these squamae the stamina in triandrous 
Grasses alternate, and they are consequently opposite to the parts of the 
proper envelope ; that is, one stamen is opposed to the axis of its lower or 
outer valve, and the two others are placed opposite to the two nerves of the 
upper valve. Hence, if the inner envelope be considered as consisting of 
bracteae, and the hypogynous squamae as forming the perianthium, it seems 
to follow, from the relation these parts have to the axis of inflorescence, that 
the outer series of this perianthium is wanting, while its corresponding sta- 
mina exist, and that the whole or part of the inner series is produced while its 
corresponding stamina are generally wanting. This may, no doubt, actually 
be the case ; but as it would be, at least, contrary to every analogy in Mono- 
cotyledonous plants, it becomes in a certain degree probable that the inner or 
proper envelope of Grasses, the calyx of Jussieu, notwithstanding the ob- 
liquity in the insertion of its valves, forms in reality the outer series of the 
true perianthium, whose inner series consists of the minute scales, never more 
than three in number, and in which an irregularity in some degree anedogous 
to that of the outer series generally exists. It is necessary to be aware of the 
tendency to suppression existing, as it were, in opposite directions in the 
two floral envelopes of Grasses, to comprehend the real structure of many irre- 
