288 



MORPHOLOGY. 



upper end. Here the nucleus divides a i;reat nianv times, and 

 linall\' (ell walls are formed, so that a tissue of considerable ex- 

 tent is formed inside the wall of tjie spore, which is ^•ery 

 different from \^'hat takes place in the ferns we have 

 studied. As the prothallium matures thesjiore is cracked 

 at the point where the three angles meet, as show-n in 

 fig. 334. The archegonia are developed in this exposed 

 surface, and several can be seen in the illustration. 



588. Embyro. — After fertilization the egg divides in .such a way 

 that a long cell called a su.spensor i.s cut oil from the upper .side, 



Jig 3v^. l""! 3o4 



Section of mature macrospore IMatuie feinalL pr thillium f rig. oj5- 



of selaginella, showing female selr^mclla just burstmc: pt-n Seedling of sela- 



protlialliuni and arcliegoTiia. iIil \ ill t mai-r s; rL exj smi^ ginella still attached 

 After Pfeffer. arc) e^ ma Vttei I Itftei to tile macrospore. 



After Campbell. 



whicli elongates and ptushes the developing enib)-ro down into the center of 

 the s[")ore, or what is now tlie lemale prothallium. Here it deri\"es nourish- 

 ment from the tissues of tiie prothallium, and eventually the root and stem 

 emerge, while a process called the " foot " is still altachetl to the prothalliuiu. 

 When the root takes hold on the soil the embyro becomes tree. 



