CRYPTOGAMS 



463 



in the formation of the male prothallium resembles that shown by the Hydro- 



pterideae. 



The macrospores in some species 



similarly begin their development 



within the sporangia. After the ^=4 



division of the nucleus-which lies _ { \^8SKtSM^ICQ}S&^ ar 



in the peripheral cytoplasm at the 



apex into daughter nuclei and their 



distribution in the apical cytoplasm, 



the formation of cell walls begins. 



In this way, progressing from apex 



to base, the spore becomes filled by a 



process of multicellular formation, 



with large prothallium-cells. At the 



same time, and proceeding in the 



same direction, there begins a further 



division of these cells into smaller 



cells. In some species the apical disc 



of tissue is formed first, and is separ- 

 ated by a thickened wall or diaphragm Kl( . 4 27 ._ sria ^ Md j tt uartwii. Female prothallium 



protruding from tlie apex of the ruptured macro- 

 sj>ore ; spm, wall of macrospore ; ar, an unfertilised 

 arehegonium ; eiiibi, emb^, two embryos, with sus- 

 pensors et, sunk in the tissue of the prothalliuni. 

 (After PFEFFER, modified, x 124.) 



itpm 



from the rest of the cavity of the 

 spore ; cell-formation occurs in this 

 later. In the tissue at the apex, con- 

 sisting of small cells, the rudiments 

 of a few archegonia appear, often even 

 before the formation of the prothalliuni has been completed. The archegonia are 

 usually not formed until the spores have been discharged from the sporangium. 



r 



Fi<;. 4'J*. tieliiyiitellu Murtensii. Longitudinal section of an embryo before its sejiaratiou from 

 the spore ; et, suspensor : w, root ; /, toot : hi. le.-ives ; Hy, lij^ules : ft, apex of stem. (After 

 I'FKKFER, x 165.) 



The wall of the spore eventually bursts at the apex, and the prothallium 

 becomes partially protruded. The fertilisation of one or two archegonia, which 



