XII 



LEPTOSPORANGIA TAC HETEROSPOREAC 



395 



The leaf lobe, as soon as its first median division is complete, 

 at once begins to form the sporocarps, each half becoming 

 transferred directly into its initial cell. In this, walls are formed, 

 cutting off three series of segments (Fig. 201, D). Next a 

 ring-shaped projection arises about it, and this is the beginning 

 of the indusium {id) or sporocarp, which bears exactly the 

 same relation to the young sorus that it does in Triclionianes, 

 and Salvinia shows the same thing. From this point the two 

 sorts of sporocarps in Azolla differ. In the macrosporic ones 

 the apical cell develops directly into the single sporangium ; in 



--n 



Fig. -zoi,.— Azolla fiUculoides (Lam.). A, Longitudinal section of a dorsal lobe of the leat", X about 

 40; «, cavity with colony of Anahirna; h, unicellular hairs; B, epidermis with stomata, X150 

 (after Strasburger) ; C, longitudinal section of young root, X225; sk, root-sheath. 



the microsporic ones it forms the columella, from which the 

 microsporangia arise secondarily. 



The development of the sporangia follows closely that of 

 the other Leptosporangiatae up to the final development of the 

 spores. The tapetum is composed of but a single layer of cells 

 in Azolla, but in Salvinia it usually becomes double.^ In both 



1 Juranyi (l). 



