692 Bancroft. — Note on Vegetative Reproduction hi 
something like the sterigmata of an Aspergillus conidiophore head. Sarauw 
mentions that there was possibly a small area in the centre of the enlarged 
rhizophore heads without root-hairs; Text-fig. 7 shows this in one of the 
tubers of S. chrysorrhizos. In one case the rhizophore seems to have con- 
tinued its growth for a short distance from this area, leaving the root-hairs 
as a lateral flange or collar near its base (Text-fig. 6 , a). 
Conclusion. 
The reproductive ‘ tubers ’ in these two species of Selaginella are funda- 
mentally similar, the differences between them being dependent upon 
physiological causes, arising from the position of the tubers on the plant. 
In 6*. chrysocaidos the tubers are at the ends of ordinary vegetative 
branches and remain at the surface of the ground, the development of 
ventral rhizophores being necessary for their attachment to the substratum. 
The leaves of these tubers, though differing in form and size from those of 
the ordinary branches, contain abundant chlorophyll. In the case of 
S. chrysorrhizos , on the other hand, the tubers are developed underground 
at the ends of filamentous, modified vegetative branches. The leaves are 
scale-like and without chlorophyll, their bases and the tissues of the tuber 
containing reserve materials, the storage of which is unnecessary in the 
chlorophyll-containing surface tubers. 
Further, in the case of S'. chrysorrhizos , both dorsal and ventral rhizo- 
phores are developed, but they remain very short, since the tubers are 
already embedded in the ground and elongation of rhizophores is not 
needed for purposes of attachment. They are fairly equally developed, 
being subjected to the same developmental conditions, and both are 
apparently functional in obtaining nutritive elements from the soil by 
means of the root-hairs developed from their enlarged ends, probably as 
a response to nutritive stimuli. 1 
The dorsal and ventral rhizophores of S. chrysocaulos , on the other 
hand, encounter different conditions from the commencement of their 
development ; for instance, the ventral rhizophores are subjected to less 
light intensity and greater humidity than the dorsal rhizophores, owing to 
the position of the tubers on the surface of the ground. The ventral rhizo- 
phores alone are functional in attaching the tubers and for nutritive 
purposes ; they attain a considerable development, while the functionless 
dorsal rhizophores are very much reduced, more so even than in S'. chry- 
sorrhizos . 
The writer desires to express gratitude to Professor Seward for per- 
1 Sarauw, 1. c., p. 65 ; the branching of the rhizophores is said to be due to the dampness of 
the ground, while the nutritive content of the medium is responsible for their further development. 
