150 THE EVOLUTION OF PLANTS 



compound spore-sac, or " synangium." In An- 

 giopteris and one other closely allied genus, this is 

 not the case; the sporangia are very closely 

 associated in two ranks to form each " sorus," 

 but are not actually joined. Even here, how- 

 ever, the sporangia are different from those of 

 most Ferns; they are larger 

 and of more solid construc- 

 tion, with a wall several 

 cells thick. The opening of 

 the sporangium to set free 

 the spores is effected by 

 means of a patch of 

 thickened cells at the apex, 

 an arrangement bearing 

 some resemblance to that 

 in the Osmundas. In the 

 other three genera, Ma- 

 rattia, Dancea and Kaul- 

 fussia, including the great 



f " 



under surface of Kaul- the sporangia are united. 



gler and Prantl. 

 SlighUy magnified. 



shaped fruits or synangia, 

 each conta i n i ng a doub l e 



row of compartments (of which there are about 

 ten in each row), representing the sporangia (see 

 fig. 17, A). In one species the whole compound 

 body is stalked, and closely resembles a compound 



