52 



MOSSES AND FERNS 



CHAP, 



The young spermatid (Fig. 17, 3) is triangular in section, 

 and the blepharoplast is situated in the acute angle which later 

 forms the anterior end of the spermatozoid. The blepharoplast 

 becomes somewhat elongated, and from it grow out the two 

 cilia before any marked change is observable in the nucleus. 

 (Fig. 17, 5). Before the cilia can be seen, there appears in the 

 cytoplasm a round body which stains strongly, but whose origin 

 is not clear. This body Ikeno calls the chromatoid "Neben- 

 korper," and says that it does not participate directly in the 

 development of the spermatozoid, but ultimately disappears. 

 His figures 30 and 31, however, look as if the portion of the 

 spermatozoid between the blepharoplast and the nucleus was 

 derived from this "nebenkorper," and not from the cytoplasm, 

 as he states is the case. 



Fig. 17. — Marchantia polymorpha. Development of the spermatozoid, i, Sperm-cells 

 from the young antheridium; 2, final division of the sperm-cell to form the two 

 spermatids; 3-7, development of the spermatozoid; b, blepharoplast; p, "neben- 

 korper"; (All figures after Ikeno). 



Owing to tlie very small size of the spermatozoids in 

 Marchantia, it could not be positively demonstrated whether 

 there is a cytoplasmic envelope about the nuclear portion of the 

 spermatozoid, but it was concluded that such probably is the 

 case. 



When the antheridia are borne directly upon the thallus, 

 the apical growth continues after antheridia cease to be formed, 

 and the receptacle is thus left far back of the growing in point. 

 In forms like Targionia, however, where there are special 

 antheridial branches, the growth of these is limited, and gener- 

 allv ceases with the formation of the last antheridia. The most 



