XLV] PLATYCERIUM 211 



(Fig. 715, a): but it is a much more pronounced feature here, even in the 

 partially fertile patch oiPlatyceritun. In a fully fertile patch the course of these 

 receptacular strands is much longer; and they may even branch, forming thus 

 an elaborate second system of venation in a plane closely within the lower 

 surface: so that the patch is "diplodesmic" (Fig. 715, b). The appearance 

 presented in transverse section is shown in Fig. 720, where the strands of 

 the two systems are seen to lie at quite distinct levels, while the sporangia 

 are attached close to the superficial receptaculai strand. The similarity to 

 what has been seen in Cheiropleuria cannot be missed, but with the differ- 

 ence that here the sori, though elongated, maintain their identity: in 

 Cheiropleuria the sporangia are spread over the whole fertile area, after the 

 manner usual in Acrostichoid Ferns, and soral identity is lost. 



Fig. 720. Transverse section of a fertile leaf of /'/a/;/c.?r?V/w 

 willmkiilsiloorQ, showing vascular strands belonging to the 

 two diplodesniic systems : the strand nearer to the upper 

 surface belongs to the main system of the lamina, that nearer 

 the lower surface is a receptacular strand. ( x 66.) 



Hofmeister {Higher Cryptogamia, p. 252) described a diplodesmic structure 

 in the humus-leaves of P. alcicorne. It is a very remarkable thing that this 

 condition of the humus-leaves should be repeated in the sporophylls, but 

 only in their fertile regions (see " Studies on Spore-producing Members," Phil. 

 Trans. Vol. 192, 1899, p. %6). It suggests that possibly all the types of leaf 

 in Platycerium sprang from a "general purposes" type. 



The dermal appendages are hairs, which are branched in a stellate 

 manner. Their origin by steps of increasing complexity, from unicellular 

 glandular hairs to the multicellular stellate state, has been traced by 

 Von Straszewski in the sporeling, where they are already present on the 

 first leaves. Scales are not described for any of the species, even upon the 

 rhizome. In this Platycerium accords with Cheiropleuria, Dipteris, and 

 Matonia. The stellate hairs are associated in particular with the sporangia, 

 as paraphyses. Sometimes they are very long and form an almost woolly 



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