THE HIGHER CRYPTOGAMIA. 395 



small * spherical cells were formed in almost every small 

 spore, and nearly filled its cavity (PI. LVII, fig. 1 3). By 

 careful pressure these cellules escaped through the fissures 

 of the ruptured spore-membranes. They contained either 

 a finely granular protoplasm,! or a very fine, thin sperma- 

 tozoon, rolled up spirally, which when free moved slowly 

 (PI. LVII, fig. 15). 



The production of spermatozoa in the small spores termi- 

 nates long before the complete formation of the prothallium. 

 In /S. helvetica, as has been said, it ceases five months after 

 the sowing of the spores, whilst the first archegonia on the 

 prothallia of large spores sown at the same time, did not 

 appear until six weeks later. This is no doubt the reason 

 why all experiments with the large spores yield no result — 

 whether sown separately or mixed with the small spores — 

 where the possibility of the subsequent access to the pro- 

 thallia of small spores of the same species, is precluded. \ 

 The young plant or embryo is formed by the repeated 

 bipartition of the one daughter-cell produced in the basal 

 cell of the archegonium. It does not often happen that 

 more than one archegonium of the same prothallium is im- 

 pregnated. The abortive archegonia, especially those low 

 down on the prothallium, often exhibit a peculiar luxuriant 

 growth of their apical cells § (PI. LVIII, figs. 4, 5). The 

 first division of the mother-cell of the embryo (the germinal 

 vesicle) takes place by a transverse septum (PI. LVIII, 

 fig. 3). || 



It happens occasionally but rarely that the embryo origi- 

 nates immediately from the lower of the two cells, and that 

 all its daughter- cells take part in the formation of the 

 massive portion of its first axis (PL LVIII, fig. 6). The 



* Diameter gjg'" or less. 



f See PI. LVII, fig. 13. I consider these cellules as not fully developed. 



% When I sowed the large and small spores together, and covered them with 

 a hand-glass, all the sowing failed. Sprint/was similarly unsuccessful ('Mono- 

 graphic de la famille des Lycopodiacees,' extraite des tomes xv et xxiv des * Me- 

 moires de l'Academie Royal de Belgique,' Bruxelles, 1842 et '49, p. 316, note). 

 On the other hand when richly-fruiting specimens of the same Selaginella were 

 brought under the hand-glass, embryos soon appeared. 



§ The process is very accurately explained by Mettenius, 'Beitrage,' Part 1, 

 p. 12. 



|| See the note to this figure in the explanation of the plates. 



