The Nature and Origin of Stipules. 23 



eluding in the widest interpretation the Characese, Bryophyta, 

 Pteridophyta and Spermatophyta. 



As, in the Characese and Bryophyta, the plant body represents 

 the gametophyte stage of development, there can be no homology 

 of the leaves of these plants with those of the Pteridophyta and 

 Spermatophyta in which the plant body is the sporophyte. Por 

 this reason the so-called stipules of the Charas, together with the 

 basal lobes or saclike and straplike appendages of the leaves of 

 many Hepaticse need not be taken into consideration. 



Accepting the general theory of evolution in nature, we must 

 admit that the origin of all the higher plants is algal, but just what 

 the relationship of the Pteridophyta to the Spermatophyta may 

 be is still an open question. The same is true in greater or less 

 degree of the affinity of the Monocotyledones, Dicotyledones and 

 Gymnospermse in the latter group. 



This question of relationship is of considerable importance in 

 connection with the problem before us as determining the homol- 

 ogy of the foliar appendages in the several groups. The evi- 

 dence in support of the doctrine of the common origin of all the 

 Angiospermse is particularly strong and may be considered as 

 conclusive. But the relationship of the Gymnospermse to the Angio- 

 spermse is more remote, and that of the Pteridophyta still more so- 

 and, though there are many points of resemblance, the similar 

 characters may be cases of parallel development rather than indi- 

 cations of a common origin. It is my present opinion, however, 

 that the Gymnospermse sprang from some generalized hetero, 

 sporous Pteridophyte,* that the early Angiospermse were differ- 

 entiated from related forms, and that therefore, the foliar organs 

 in the three groups may be considered as homologous. But this 

 homology can apply to the leaves of Pteridophytes in a very 

 general way only, namely, to such undifferentiated forms of leaves 

 as the ancestors which gave rise to the early Gymnospermse and 

 Angiospermse may be supposed to have had. While, therefore, 

 the foliar organs in the three classes are to be considered homol- 

 ogous in their origin, they cannot be so considered in their dif- 

 ferentiation and the evolution of leaf-forms in the Pteridophyta 

 and Gymnospermse, though analogous in many points to their 

 evolution among the Angiospermse, should be regarded as inde- 

 pendent. "We may then consider the " stipule " of the Ophio- 



* See Campbell, Mosses and Ferns, 300. 1895. 



