254 
ORGANOGRAPHY. 
BOOK I. 
tion macropodal. In these ideas, however, Richard was wrong, 
as is now well known. 
From what has been stated, it is apparent that dicotyledons 
are not absolutely characterised by having two cotyledons, 
nor monocotyledons by having only one. The real distinction 
between them consists in their endorhizal or exorhizal ger- 
mination, and in the cotyledons of dicotyledons being opposite 
or verticillate, while they are in monocotyledons solitary or 
alternate. Some botanists have, therefore, recommended the 
substitution of other terms in lieu of those in common use. 
Cassini suggests isodynamous or isohrious for dicotyledons, 
because their force of developement is equal on both sides ; 
and anisodynamoiis or anisobrious for monocotyledons, because 
their force of developement is greater on one side than on the 
other. Another writer, Lestiboudois, would call dicotyledons 
exoptiles, because their plumula is naked ; and monocotyle- 
dons endoptiles^ because their plumule is enclosed within the 
cotyledon; but there seems little use in these proposed changes, 
which are, moreover, as open to objections as the terms in 
common use. 
In the Library of Useful Knoidedge an apparently just 
explanation of the analogy between the embryo of monoco- 
tyledons and dicotyledons has been given ; and I take the 
liberty of reproducing it here : — 
“ 1. The embryo of an Arum is like that of a Palm, only 
there is a slit on one side of it through which the plumule 
easily escapes; 2. in Rice (Oryza) this slit is very much 
lengthened and widened; 3. in Barley the plumule projects 
beyond the slit, leaving a flat cotyledon on one side; and, 
4., in Wheat the embryo has the structure of Barley, with 
this most important exception, that at the base of the plumule 
in front there is a rudimentary cotyledon, alternate with the 
large flat one, on the opposite side of the plumule. Hence 
we are to infer that the monocotyledonous embryo of a Palm 
is analogous to that of a dicotyledon^ of icfiich one of the cotyle- 
dons is abstracted^ and the other rolled round the plumula and 
consolidated at its edges. And this is the view that must be 
taken of the monocotyledonous embryo in general, all the 
modifications of which seem reducible to this standard. 
