PH^EOPHYCE^E 



103 



interstitial cells of the thallus which divide 

 up transversely and longitudinally to form pluri- 

 1 ocular sporangia. These occur generally in numbers 

 adjacent to each other. The other kind, which 

 appear to be more common, arise by a process from 

 a superficial cell (or one of the cells where the 

 thallus consists of a single row). This process divides 



FIG. <>-i. Kjellmania sori- 

 fera. Filament with young 

 sorns sporangia. Highly mag- 

 nified. (After Rcinke ) 



FIG. 26. Stictyosiplion DecaisneiL 

 Transverse section of thallus showing 

 sporangia. Highly magnified. 



up by walls running transversely to the axis of 

 the plant into a sorus of cells, each of which ac- 

 quires an arched apex and divides farther into 2-4 

 loculi one above the other. Each loculus produces 

 a single zoospore. The whole sorus is thus in this 

 case the product of a single superficial cell. The 

 occurrence here and in Giraudia of two kinds of 



