XXXIX] CHEILANTHES 89 



The sori contain each a relatively small number of sporangia, which are 

 long-stalked at maturity, but with other features similar to those of Pellaca 

 or NotJiolaena. There is again some diversity in spore-numbers: the highest 

 counts are in C. vestita Sw. and Fendleri Hk., which point to a typical 

 number of 48 to 64. But in a number of other species, including the 

 anatomically advanced C. gracilliina and uliginosa, the counts indicate 

 numbers ranging from 24 to 32 (Marsh). The parallelism of progression 

 between anatomy and spore-number is worthy of note. There is no perispore. 



The question of actual origin of the sori in the Cheilanthoid Ferns has 

 been left aside by most systematic writers: and yet such facts appear 

 essential to the determination of their affinity. The main questions are 

 whether the sporangia are superficial or marginal in origin, and whether 



Fig. 643. Vertical sections of the young fertile pinnule of Cheilanthes tnicrophylla Sw., showing that the 

 indusioid flap is of marginal origin, and the sporangia (s) definitely superficial. ( x 200.) C = a younger, 

 D = a. more advanced state. 



there is any sign of an inner or lower indusium. The facts have been 

 ascertained for C. viicropJiylla Sw., a species from the section Eu- Cheilanthes, 

 with finely divided leaves, roundish sori, and a narrow pale "involucre." 

 Since here the adult sori are seated close to the margin, their development 

 should give evidence of value as to the relation of the sorus to the marginal 

 segmentation. Sections of the very young pinnule show clearly that the 

 segmentation leads continuously to the marginal flap: thus the "involucre" 

 or "indusium" represents the actual margin itself. It becomes strongly 

 reflexed as it develops, corresponding in this to the reflexed flap oi Adiantum 

 or Pellaea. The first sporangia arise as superficial outgrowths of single cells 

 at points well within the margin, which at once overarches them (Fig. 643). 

 In this species there is no definite sequence in the production of the few 

 sporangia- but Horvat (1925) finds in C. ptcridioidcs (Reich.) C. Chr. 



