XLiv] BRAINEA 177 



wide apart, and quite distinct from one another: in fact there is no com- 

 missure linking the veins together, as is usual in Blechnuin. The sporangia 

 arise from the whole surface intervening between them : the condition is 

 distinctly Acrostichoid. Often there is no sign of a flange in Stettochlaena 

 (Fig. 699, 17, a-c): occasionally, however, a vestigial outgrowth may be 

 found {e,f). 



The sporangia of Stenochlaena are fair examples of those of Blechnoid 

 Ferns (Fig. yoo,A — D). They are structurally intermediate between the type 

 with obliquely continuous, and that with vertical and interrupted annul us. 

 It will be clear that they are not far removed from the type with a continuous 

 oblique ring, such as is seen in Matteuccia^ where, as here, the number of its 

 cells is high (Fig. 700, E). They are in fact just such sporangia as might have 

 been anticipated, following the analogy of other Ferns which have passed 

 from a gradate ancestry to a mixed state of the sorus. The cumulative effect of 

 all the evidence, foliar morphology, anatomy, soral and sporangial structure, 

 is to show that Stenochlaena is a Blechnoid type which has assumed a 

 climbing habit and an Acrostichoid, non-soral state. 



Fig. 69S. Stenoclilacim sorbifolia : transverse sections of the stock 

 a and b show different sizes and complexities of structure. 



Brainea J. Sm. 



This monotypic genus is represented by a small Tree-Fern, B. insignis 

 (Hk.) J. Sm., from China, of Blechnoid habit. Anatomically it resembles 

 advanced members of the group, with a dictyostele giving off leaf-traces each 

 originating as two straps, which divide upwards to form some 10 or 12 

 strands. It bears scales and mucilaginous hairs. The leaves are all alike, but 

 the fertile pinnae are narrower with crinkled margins. There is no indusial 

 flap, and the sporangia spread over the lower surface, but stop short of the 

 margin. The venation is for the most part open, but with occasional fusions, 

 after the type of Doodia (Vol. I, Fig. 94, /). The apex of a fertile pinna 

 suggests the origin of the Acrostichoid state (Fig. 701, 18). The distal veins 



