HOEMEISTER, ON THE HIGHER CRYPTOGAMIA. 329 



and are carried up to the surface of the water in the early 

 spring by the surrounding growing masses of confervas. In 

 the last weeks of March a short three-edged cellular body 

 of a beautiful emerald-green colour is seen at the apex of 

 the spore, between the three separated lobes of the outer 

 spore-membrane. This body is the prothallium. 



The prothallium is produced by continued bi-partition of 

 the agglomeration of granular mucilage which was spread 

 over the arched apex of the interior of the spore, and has 

 become transformed into a flattened cell (PI. XLV, fig. 1). 

 The prothallium whilst still very young is already multicel- 

 lular, and exhibits a simple cellular layer, spread over the 

 inner arcuate cavity of the macrospore (PI. XLV, fig. 3). 

 When seen from above it appears to have a bluntly trian- 

 gular form (PI. XLV, fig. 4). From the arrangement of 

 the cells it may be concluded, that when the primary mother- 

 cell was first divided by septa perpendicular to the mem- 

 brane of the macrospore, a three-sided and a four-sided 

 moiety were normally formed upon each division. As soon 

 as the middle of the prothallium, by transverse division of 

 its cells, has attained a thickness of three cellular layers, the 

 first archegonium is formed at its apex. The position of the 

 cells of the prothallium which at this time is still entirely 

 enclosed by the lobes of the spore-membrane and is devoid 

 of chlorophyll when seen in longitudinal section, shows 

 clearly that this first archegonium was formed by transverse 

 division occurring twice in the middle cell of the prothallium. 

 The middle of the three daughter-cells becomes the central 

 cell of the archegonium. At first it is much drawn out in 

 width and is almost tabular (PI. XLV, fig. 5). The upper 

 cell first divides twice by longitudinal septa arranged cross- 

 wise. The four daughter-cells are afterwards, and after 

 their free outer surface has become arched, divided by trans- 

 verse septa (PL XLV, fig. 6). By parting asunder at their 

 edges of contact they form the canal leading to the central 

 cell. In the lower one of the three cells which are derived 

 from the middle cell of the prothallium, the cell-multiplica- 

 tion which prevails in the entire mass of the prothallium is 

 continued, and by this means the circumference of the latter 

 is considerably enlarged, and thus some time after the 



