320 HOFMEISTER, ON 



entire cavity of the sporangium, which in the mean time 

 has become much enlarged. The shape of the spore changes 

 during its growth from that of a globe into a short pear- 

 like form (PL XLIV, figs. 12, 13, 14), and from the latter 

 into that of an oval, slightly constricted at the equator 

 (PI. XL1II, fig. 1). In its narrow end, which is turned 

 towards the apex of the sporangium, its nucleus is found 

 embedded in a mucilaginous layer which clothes the wall. 



By the time the spore has become globular a transparent 

 outer membrane is distinguishable, differing from the deli- 

 cate inner wall. Afterwards a second membrane, composed 

 of prismatic closely appressed columnar cells, is formed 

 upon this inner layer of the outer membrane. These 

 columnar cells are very short at the base of the spore, much 

 longer in its upper third part, but altogether wanting at 

 the apical point of the spore. The ripe spore is clothed by 

 a thick gelatinous layer, the component parts of which are 

 also prism-shaped. This layer also does not cover the apex 

 of the spore, to which there is access by a funnel-shaped 

 passage through the gelatinous layer (PI. XLIII, figs. 1, 7). 

 The glassy inner layer of the outer membrane extends 

 beyond the apex of the ripe spore in the form of a 

 conical arch, open at the tip. It appears torn into nu- 

 merous in Pilularia glohullfera as many as eight three- 

 sided shreds. 



The spores which originated in the upper sporangia 

 are transformed jointly and severally into much smaller 

 globular spores, exhibiting at their apices three fissures 

 of the exosporium, meeting at angles of 120. These 

 fissures point out the edges of contact of four spores 

 inside a set of special mother-cells. In Pilularia minuta 

 the small spores also are clothed w T ith a gelatinous layer, 

 which is wanting in those of P. globulifera. No trace 

 of a nucleus is visible either in the large or small spores 

 when ripe. The contents of both consist of a mass of 

 albuminous fluid containing numerous firm granules of a 

 substance rendered brown by iodine, as well as oil-drops 

 and starch -grains. In the large spores the starch-grains, 

 which are of a great size, exhibit manifest lamination, and 

 a central cavity with fissures proceeding from it. In the 



