XL] PERANEMA 109 



condition of the sporangia is attained early, and there is no regularity of 

 their orientation in the sorus such as is usual in gradate Ferns. 



The development of the sorus as a whole was traced by the late Dr Davie 

 {Ann. of Bot. XXVI, p. 245 and XXX, p. 102), from whose work Fig. 653 is 

 taken. But a re-examination of his preparations, and particularly that from 



Fig. 653. Immature soius of Pcranema in vertical section, with 

 stalk fully developed. The indusium covers the spherical recep- 

 tacle to which a vascular strand passes up the stalk. A narrow- 

 slit is seen between the stalk and the margin of the indusium, 

 on the left side, which is directed towards the leaf-margin. The 

 sorus is " mixed," but with traces of a basipetal sequence at first. 

 a, (5 = intercalated stalk. (After Davie. X65.) 



