[ 565 j 
XX. On the Comparative Morphology of the Leaf in the Vascular Cryptogams 
and Gymnosperms. 
By F. 0 . Bower, M.A., F.L.S. 
Communicated by W. T. Thiselton Dyer, M.A., C.M.G., F.R.S. 
Received May 13,—Read May 29, 1884. 
[Plates 37-40.] 
Introduction. 
The origin of the tendency among the earlier morphologists to draw a sharp distinc¬ 
tion between stem and leaf may most probably be traced to the fact that vegetable 
morphology was first pursued as a science in regions where deciduous trees prevail. 
Seeing the leaves of so many plants fall off as a whole, while the scar left w T as almost 
a direct continuation of the external surface of the stem, doubtless gave rise to the 
view that the two should be regarded as radically distinct members. 
As the science of morphology progressed it became necessary, if this distinction 
were to be maintained, to define more clearly how members belonging to these two 
categories differ one from another. Various attempts were made by authors to show in 
what the essential difference consisted, the most notable being that of Hofmeister,'* 
who brought forward a number of distinctions, based chiefly upon development. 
The most essential of these were adopted in that section of the Text Book of 
Sachs,! which deals with the relations of leaves and leaf-forming axes. In the last 
paragraph (No. 8) of that section, he clearly lays down the principle that “ the 
expressions stem and leaf denote only certain relationships of the parts of a whole— 
the shoot.” This principle is elaborated in his more recent lectures,J in which he 
writes as follows :—A typical shoot consists of the leaves and the axis, which 
however are not really to be regarded as different organs, but fundamentally as parts 
only of one organ. In their nature, and as shown by the history of their 
development, the leaves are fundamentally nothing more than processes, or out¬ 
growths of the axis of the shoot.” If we accept these propositions, and I 
do not see how we can do otherwise, the same method of morphological treatment 
* Allgemeine Morphologie, pp. 406-416. 
f Second English Edition, p. 153. 
| Vorlesnngen, p. 48. 
