GENERAL MORPHOLOGY 



443 



not an uncommon thing for sporangia to appear upon the sterile leaf: an 

 example of this is shown for B. simplex in Fig. 240 M, but it is more 

 clearly shown in specimens of B. Lunaria (Fig. 242). Moreover, not a 

 part only, but even the whole of the normally sterile lamina may be thus 

 occupied, and Goebel quotes a locality on the Ostsee where this condition 

 has become constant. 1 The importance of this from a theoretical point 

 of view will be discussed later. 



Botrychium Lunaria. Steiile laminae, which occasionally produce sporangia (sp) on 

 certain pinnae, and have partly or wholly assumed the form of the fertile spike \f in 

 B and C is the fertile spike itself. Natural size. (After Goebel.) 



The third genus, Helminthostachys, differs from the others in having a 

 creeping rhizome, which is markedly dorsiventral, bearing the leaves in two 

 rows on its upper surface, while the roots spring from its flanks and under 

 surface (Fig. 243). The individual roots are not definitely related to the 

 leaves either in number or position, a condition comparable with 

 Botrychium rather than with Ophioglossum : they branch monopodially, and 

 are hairless. The rhizome is normally unbranched- and perennial, serving 



1 Schenk's Handlnich, vol. iii., p. 112. 



2 Farmer (Ann. of Bot., xiii., p. 423) found that adventitious branches were frequently 

 seen on old, almost decorticated parts of the rhizome of Helminthostachys, Gwynne- 

 Yaughan (Ann. of Bot., xvi., p. 170) has described how in the axil of each leaf, and 

 even of the leaves of young seedlings, a narrow oblique invaginated channel leads 

 through the cortex to a point just outside the stele, at the upper limit of the leaf-gap. 

 A mass of parenchyma, covered in except at its apex by an extension of the endodermis, 

 and terminated by a small, obliquely truncated, conical projection extends outwards from 

 the stele to meet this invaginated channel. He suggested that these structures represent 

 vestigial axillary buds, and that possibly the ancestors of Helminthostachys branched 

 more copiously than the present plant. Gwynne-Vaughan's recognition of their bud- 

 character received its full justification by the discovery of similar bodies in J-i at rye hi urn 

 Lunaria by Bruchmann (Flora, 1906, p. 226), which actually develop into lateral 

 branches. He found them present chiefly upon young plant*, and traced their origin 

 each from a single superficial cell of the rhi/.ome : they occur especially where the axis 



