FILICINEJE, 



457 



macrospore — increases very much in size whilst the other three gradually shrivel. 

 Figures 323 and 324 illustrate the development of the macrospore of Pilularia 

 globult/era, after drawings made by me in 1866. They show the young macrospore 

 in /, //, III, still in connexion with its three sister-cells which are invested by the 

 cell-wall of the m.other-cell which has already become mucilaginous (7). The four 

 cells are attached to each other by means of rigid spine-like projections, that of the 

 macrospore being the most strongly developed. At a later period the macrospore is 



Fig. 322. — Development of the sporangium of /"z'/w/arza 

 globulifera, all the figures in optical longitudinal section ; 

 JV c primary mother-cell of the spores invested by the 

 tapetum ; sm mother-cells of the spores (X 5So). 



Fig. 323.— Development of the macrospore of Pilularia 

 globulifera ; x the abortive sister-cells, nt the macrospore, A' its 

 nucleus, a the inner, b the outer coat. 



of very considerable size; its aborted sister-cells are attached to it laterally (Fig. 

 324, x), and its firm coat has become brown and is invested by a layer of mucilage 

 (Fig. 323, IV, b) which often appears to be folded. It forms a papilla (Fig. 324, b') 

 at the apex which shrivels when the spore ripens. A layer of a soft substance, 

 presenting a distinctly prismatic structure, makes its appearance (Fig. 324, C) on the 

 outside of the mucilaginous layer, and becomes in its turn invested by a third layer 

 which is thicker than itself of a less distinctly organised structure. Both these layers 

 leave the apex of the spore uncovered and form a funnel through which the 



