XIV ISOETACE^ 541 



out of the oil. Scattered through the cytoplasm are round 

 starch granules with a central hilum. The large nucleus lies 

 in the basal part of the spore. It is broadly oval in outline, 

 and the cytoplasm immediately about it is nearly free from large 

 granules. Before germination begins there are few chro- 

 mosomes, and the nucleolus does not stain readily. 



In /. lacustris (Farmer (2)) the primary nucleus is at the 

 apex of the spore, and this is also the case in /. Malinverniana 

 (Arnoldi (i)). 



After the spores have lain a few days in water, the nucleus 

 increases in size, and then the nucleolus stains very intensely 

 and the chromosomes become more conspicuous. The nucleus 

 divides while still in its original position, and undergoes division 

 in the usual way. A very evident cell plate is formed in the 

 equator of the nuclear figure (Fig. 311, A), but no cell wall is 

 found, and the result of the division is two large free nuclei. 

 The next youngest stage observed (Fig. 311, B) had four free 

 nuclei, which now had moved to the ventral side of the spore. 

 These are very much smaller than the primary one, but are 

 relatively richer in chromatin. They continue to divide until 

 there are from about thirty to fifty free nuclei, but as yet no 

 trace of cell division can be seen. Most of the nuclei lie in 

 the ventral part of the spore, close to the outer wall, but an 

 occasional one may be detected elsewhere. 



Cell division begins at the apex (ventral part) of the spore. 

 At this time the cytoplasm stains more deeply than before, 

 and sometimes extremely delicate threads may be detected, 

 radiating from the nuclei and connecting adjacent ones (Fig. 

 311, C). The first traces of the division walls appear simul- 

 taneously between the nuclei in the form of cell plates composed 

 of minute granules, probably of cellulose, which quickly coalesce 

 and form a continuous membrane. In this way the upper part 

 of the spore becomes transformed into a solid tissue (Fig. 312). 



The formation of the cell walls closely resembles that in 

 Selaginella. The primary cells, or areoles, are open in their 

 inner faces, and it is not until the second nuclear division takes 

 place that the inner cell wall is developed. (Arnoldi ( i ), Figs. 



5,6). 



The cell formation proceeds quickly toward the base of the 

 spore, following the spore wall, so that for a time the central 

 space remains undivided. The whole process recalls most 



