212 



SYMMETRY OF THE SPOROPHYTE 



. 





X. 



FK;. 107. 



Diagrammatic representation of the end of a 

 rhizome of Kautfnssia. iu = wings of stipule; 

 Cinu = transverse commissure. (After Gwynne- 

 Vaughan.) 



in all the genera of Marattiaceae investigated hitherto is upright, bursting 

 through the prothallus, not recumbent as in other Ferns (Fig. 105). In 



Angiopteris and Marattia this con- 

 dition is maintained throughout life, 

 and there is no reason to think other- 

 wise than that these plants retain 

 their primitive position. It is probably 

 shared also by Archangiopteris : l at 

 all events there was no dorsiventrality 

 in the only specimen with an axis 

 hitherto examined. In the genus 

 Danaea the same holds for D. 

 simplidfolia ; but certain other species 

 of Danaea have an oblique rhizome, 

 for instance, Danaea alata (Fig. 106). 

 Comparison of a number of stocks of 

 this Fern shows various degrees of 



inclination and curvature of the axis. It is upright at first, and produces 

 leaves and roots uniformly on both sides of the axis ; but later the axis 

 arches over to one side, and a distichous arrangement of the leaves is 

 approached, while the roots originate chiefly from 

 the side directed downwards. In Kanlfussia these 

 characters are more pronounced ; for there the 

 mature rhizome is horizontal, with marked dorsi- 

 ventrality, and with internodes of appreciable 

 length (Fig. 107). Unfortunately the early 

 development of the sporophyte of Kanlfussia is 

 still unknown. It seems a reasonable interpre- 

 tation of the facts that the upright position, with 

 radial symmetry, as seen in Angiopteris and 

 Marattia, was the primitive condition here as in 

 other Vascular Plants : and that the oblique 

 position, already seen in certain Danaeas, became 

 more accentuated in the horizontal rhizome of 

 Kaulfussia, with its marked dorsiventrality. 



The analogy with what is seen in the Ophio- 

 glossaceae greatly strengthens this conclusion. As 

 in the Marattiaceae, so also in all the genera of 

 the Ophioglossaceae the axis is from the first 

 upright (Fig. 108) ; and that position is maintained 



throughout life in Ophioglossum and Botrychium. But in Helminthostachys, 

 notwithstanding its originally vertical position, the axis of the mature 

 plant is markedly dorsiventral (Fig. 109), with distichous arrangement 

 of the leaves. The conclusion which naturally follows is that in the 



1 Gwynne-Vaughan, Ann. Bo/., \i\., p. 260. 



v 



I 



i 



I'M,. 108. 



H elminthostachys seylanica. 



YOIIII.L; plant attached to pro- 

 thalln.s. Natural >i/e. (. \fl<-r 

 Lang.) 



