47 i 
the Monocotyledonous Leaf. 
between the ‘ laminae ’ of Monocotyledons belonging to widely separated 
Families, and also a decided difference between such laminae and those of 
the Dicotyledons. It is not easy explicitly to define these resemblances 
and differences, but one or two of the more obvious points maybe indicated. 
The prevalence of forms tending towards the sagittate or cordate—such as 
those which occur in the Alismataceae ( Sagittaria ), Pontederiaceae ( Mono - 
ckoria), Liliaceae ( Smilax ), Dioscoreaceae ( Tamus ), Araceae {Arum), 
and Orchidaceae ( Nervilia )—becomes less inexplicable if we regard all 
these laminae as owing their skeletal form to the gradual separation 
of the originally parallel, petiolar veins. The similarity in the peculiar 
mode of dissection of the leaves of the Palmae, 1 Cyclanthaceae, and 
certain Araceae is also a striking feature, since these Families are by no 
means closely related. Their leaves become more or less deeply incised or 
actually compound, by a process of necrosis or tearing along certain lines. 
This method is in no way homologous with the mode of origin of a com¬ 
pound leaf among the Dicotyledons; it suggests that the foliar member 
exhibiting it may be in an experimental stage of evolution, and that, if 
we may so express it, it lacks^ the capacity for forming lobes or pinnae, 
which is part of the inherited equipment of a Dicotyledon. The tearing 
into strips, which is constantly suffered by the leaves of the Musaceae, is 
generally interpreted as an adaptation to a windy climate. But it may, 
perhaps, rather be regarded as another indication that the ‘ lamina ’ of 
a Monocotyledon is a somewhat imperfect organ, which only succeeds by 
cumbrous means in approximating to those complex forms which are 
reached in the Dicotyledons by direct and economical paths. 
The greatest difficulty in the way of Henslow’s extension of the phyllode 
theory seems to be that there is very great similarity between the leaf- 
blades of certain Ranunculaceae and of some of the Alismataceae, although 
these organs must be supposed, on this theory, to have had a different 
origin. De Candolle 2 suggested that the leaves of such a plant as Ranun¬ 
culus gramineus , L., might be interpreted as phyllodic, but this view is 
scarcely borne out by a comparative study of the Family. The nervation 
throughout the Ranunculaceae is on a uniform plan—'the simple, Alisma- 
taceae-like leaves being connected by a series of intermediate forms with 
the more typical cases, which show no obvious resemblance to Mono¬ 
cotyledons. 3 The simpler leaves among the Ranunculaceae may thus be 
interpreted, not as the more primitive of the types found in the Family, 
but as reduced forms—an interpretation which minimizes the significance of 
their resemblance to the ‘ laminae 5 of the Alismataceae. 
The phyllode theory has met with lively opposition at the hands of 
Goebel. 4 He discusses the question chiefly in connexion with Sagittaria , 
1 Trecul, A. (1853). 2 Candolle, A. P. de (1827)'. 
3 Bitter, G. (1897). 4 Goebel, K. (1891-3). , 
