BOTRYOPTERIDEAE 343 



and if we consider the axillary shoot of the latter, 

 where the stele has a simple bilateral structure, 

 the agreement is almost exact. The protoxylem of 

 T. reniforme is placed internally, forming two groups, 

 accompanied by parenchyma, vvhile^small elements also 

 occur at the periphery of the wood, where they are 

 connected with the insertion of adventitious roots. ' In 

 other species, however, the protoxylem may be wholly 

 peripheral {e.g. T. scandens) or scattered {e.g. T. spicatuni). 

 The leaf-trace gives off the stele of the axillary branch 

 precisely in the same manner as in Zygopteris, the 

 resemblance extending even to details. It would be 

 rash to push the comparison too far, but, from an 

 anatomical point of view, there is no doubt that the 

 Hymenophyllaceae show the closest analogies with 

 the genus Zygopteris, and especially with those species 

 which have axillary branching. With Botryopteris 

 there is also a general agreement, though a much less 

 close one. As Mr. Boodle says (Joe. cit. p. 489), "The 

 solid stele of Botryopteris, as the wood consists of 

 tracheides only, resembles the stele found in the lower 

 part of the seedling-stem of Trichomanes rather than 

 the solid stele of T. spicatum, etc." The general 

 analogy between Botryopterideae and Hymenophyl- 

 laceae was early recognised by Renault. It is, however, 

 improbable that anything more than a remote affinity 

 is indicated by the analogies referred to. 



As already pointed out, there is a fairly sharp 

 distinction between the anatomy of the Botryopteris 

 type and that represented by Zygopteris. The former, 

 so far as the stem is concerned, is perhaps the 

 simplest in any known vascular plant, though many 



