318 



GENERAL BOTANY 



GAMETOPHYTES AND EMBRYO 



The spores of Selaginella begin the process of germination 

 while they are still retained in the sporangium and are being 

 nourished by the mother sporophyte. The germination process 

 differs from that of the ferns and equiseta also in that the entire 

 process takes place within the spore coat and results, therefore, 

 in rudimentary gametophytes, which are permanently retained 



StroUlus Megasporophylls Strobilus MicrosporopJiyllsi 



Sporangia and' spores axis Sporangia and spores 



- -MicrosporopJiyll 

 iMicrosporangium 



FIG. 183. Spore production in Selaginella 



A, strobilus with megasporophylls and megasporangia ; B, megasporophyll with 



sporangium and spores; C, median long section of a strobilus; D, microsporophyll 



with sporangia and spores 



in the male and female spores. The female gametophyte is ulti- 

 mately exposed to the air by the rupture of the large mega- 

 spore along three lines of weakness in the spore coat, which thus 

 exposes the gametophyte and the archegonia in preparation for 

 the fertilization process (Fig. 184, a, 6). The germinated female 

 spores may still be retained in the sporangium or they may be 

 shed upon the earth, where the archegonia and gametes go 

 through the same preparatory stages for receiving the male 

 gametes as we have already described in the mosses and ferns. 

 Meanwhile the rudimentary male gametophytes are developed 

 inside of the microspores ; each of these consists essentially of a 

 small cell representing the male gametophyte, and of an anther- 

 idium composed of wall cells and of several sperm mother cells 



