30 THE MORPHOLOGY OF PTERIDOPHYTES 



as rhizomes, could have been gametophytes. Against this 

 view, however, is the fact that no archegonia or antheridia 

 have yet been convincingly demonstrated. 



Rhynia Gwynne-Vaughani (Fig. 4G) was a smaller plant 

 than R. major, attaining a height of only 20 cm. It was 

 similar in having a creeping dichotomous rhizome with 

 groups of rhizoids, but the aerial parts of the plant differed 

 in several respects ; small hemispherical lumps were scattered 

 over the surface and, besides branching dichotomously, the 

 plant was able to branch adventitiously. An interesting 

 feature of the adventitious branches was that the stele was 

 not continuous with that of the main axis. It is possible that 

 they were capable of growing into new plants if detached 

 from the parent axis, thereby providing a means of vegeta- 

 tive propagation. The sporangia were only 3 mm long and 

 the spores, too, were smaller than those of i?. major. In other 

 respects (internal anatomy, cuticle, stomata, etc.) the two 

 species were very similar indeed. 



Horneophyton Lignieri (Fig. 4I) was smaller still, its aerial 

 axes being only some 13 cm high and only 2 mm in maximum 

 diameter. It was first described under the generic name 

 Hornea, but in 1938 it was pointed out that this name had 

 already been used for another plant and a new name was 

 proposed, Horneophyton. The aerial axes were like those of 

 Rhynia major, in being quite smooth and in branching 

 dichotomously without any adventitious branches. In its 

 underground organs, Horneophyton was very different, for 

 it had short lobed tuberous corm-hke structures. From their 

 upper side aerial axes grew vertically upwards and on their 

 lower side were unicellular rhizoids. The stele of the aerial 

 axis did not continue into the tuber, which was parenchy- 

 matous throughout. Most of the tubers contained abundant 

 non-septate fungal hyphae, whose mode of life has been 

 the subject of some speculation. By analogy with other 

 groups of pteridophytes, it is commonly supposed that there 

 was a mycorrhizal association but, as Kidston and Lang^*^ 



