XXXVIII] 



LONCHITIS 



47 



Fig. 6i I. Vertical sections through the young sorus of Paesia viscosa St Hil. 

 A—d. young sorus with upper indusium consisting of two or more layers of 

 cells: the lower indusium is absent. The section follows a vein till it ends at 

 the junction with the commissure. Only one sporangium is present. B — ^ 

 similar section traversing the commissure and sorus, showing one sporangium 

 covered by a well-developed upper indusium : the lower is much feebler, and 

 represented in section by a row of cells. C=a more advanced sorus, showing 

 upper and lower indusia overlapping, two sporangia with suggestion of basi- 

 petal succession, and two hairs. ( x 75.) 



another before detachment from the stele, a state seen in Pteris cretica. 

 Both plants are hairy; but whereas L. mirita has only hairs, there are 

 numerous narrow scales on the stock of L. hirsuta. On the other hand, 

 whereas L. hirsuta has an open venation, that of L. aurita is coarsely 

 reticulate (Fig. 612). The soral characters are the same for both. The sori 

 are protected by a thick flap of the upper indusium, and the receptacle bears 

 sporangia of mixed ages, interspersed with hairs. The position of the lower 

 indusium is occupied by about two ranks of hairs, suggesting a resolution 

 of the indusium into independent cell-rows. The absence of a continuous 

 lower indusium led various authors to place these Ferns under Pteris. It is 

 just these intermediate states which provide the basis for close phyletic 

 sequences. In vascular characters in investiture, in venation and in soral 



