the Anatomy of the gemcs Selaginella , Spr. 85 
distinguished both by their greater size and more granular 
and denser protoplasm, as well as by their conspicuous bulging 
into the angle between the stem and leaf. In this view I am 
supported by Bower’s figures illustrating the development of 
the sporangium (/. c. PL 47, Fig. 79). As in wS. spinosa , the two 
primary cell-rows undergo transverse segmentation, so as to 
isolate a set of sheathing-cells surrounding the foot of the 
ligule. The outer cell-segments then separate another set 
of large comparatively empty cells, which grow in size as 
the ligule develops. Rapid segmentation of the apical region 
then takes place so as to form a thick swollen portion, which 
later becomes two-layered, and' finally ends in a unilamellar 
apical plate. In the ligules of the vegetative leaves the 
sheathing and the glossopodial cells remain in two rows, but 
in the ligules associated with sporangia both sheathing and 
glossopodial cells may divide so as to form three rows, at all 
events in the thicker median region of the ligule. 
All the observations I have made on the development of 
the ligules of other species point to a similar embryonic 
history, and I feel convinced that the number of cell-rows in 
the adult glossopodium will give a fairly reliable indication of 
the number of primary merismatic cell-rows which take part 
in the formation of the ligule, though doubtless secondary 
divisions may occur in these, as I have already pointed out in 
5 . spinosa . 
C. The Function of the Ligule. 
The homologies and functions of the ligules in the genus 
Selaginella have for long been matters of controversy. It has 
been suggested, for instance, that the ligule may be of the 
nature of an indusium, a view against which many and 
obvious objections may be raised. McNab (l.c.) considered it 
as an organ of absorption, basing his conclusion on the close 
association of the ligule with the vascular bundle of the leaf. 
A homology between the ligules of Selaginella and of Isoetes 
has been made much of by many writers, and has, as is well 
known, been employed as a basis of classification ; but, as 
