XIV LYCOPODINE.E 487 



an apical cell. The latter divides twice more, forming three 

 segments, so that the young antheridium at this stage 

 consists of eight cells arranged in two symmetrical groups. 

 Of the three segments formed in each apical cell, the 

 first and sometimes the second form periclinal walls, so that 

 a central cell (or two cells) is formed in each half of the 

 antheridium, not unlike what obtains in Marstlia^ and the 

 young antheridium consists now of two (or four) central cells 

 and eight peripheral ones. Belajeff states that the cell walls 

 do not show the cellulose reaction, and that they are later 

 absorbed. Where there are four primary central cells, these 

 by further divisions produce a single cell-complex, which, after 

 the disintegration of the peripheral cell walls, floats free in the 

 cavity of the spore. Where but two primary central cells are 

 formed, each produces a separate hemispherical cell mass. 

 Belajeff does not state the number of sperm cells formed. 

 The spermatozoids (Fig. 253, G) are extremely small and 

 closely resemble those of many Bryophytes, as well as Lyco- 

 podimn. Like these they are always biciliate. 



TJie Macrospore and Female ProtJiallium 



The formation of the female prothallium begins while the 

 spore is still within the sporangium, and long before it has 

 reached its full size. The earliest division of the primary 

 nucleus was not seen, but it is undoubtedly much the same 

 as in Isoetes, with which Selaginella closely agrees in the 

 development of the prothallium. The young macrospore is 

 quite transparent, and in the living condition is colourless and 

 shows plainly the single large globular nucleus. The youngest 

 stage, of which successful preparations were made, is shown in 

 Fig. 254, B. The spore here had reached about half its final 

 diameter, and was remarkable for the very small amount of 

 protoplasm it contained. This formed a very thin layer close 

 to the wall, much as in the embryo-sac of the Spermaphytes. 

 In this protoplasmic layer were embedded a number of some- 

 what flattened nuclei, but as yet there was no trace of cell 

 division. The central cavity appeared absolutely empty, and 

 doubtless in the living spore is filled with a watery fluid. The 

 relation of the nuclei to the primary nucleus could not be 

 traced, but in all probability it is the same as in Isoetes. In 



