/ 



ALTERNATION OF GENERATIONS 153 



the occurrence of this form among the very oldest remains 

 of land plants (Lower Devonian) hitherto known is very 

 surprising, for, excepting some cases of doubtful inter- 

 pretation, moss capsules had not been recorded from any 

 horizon earlier than the Tertiary. This was always a 

 stumbling block to the morphological theorist. But now, 

 in the presence of this proof of the extreme antiquity of 

 the Bryophyte type, he will see new possibilities open 

 before him of the origin of vascular plants from some 

 moss-like ancestry. Dr. Halle's discovery will certainly 

 bring the Bryophytes again into prominence in theories 

 of descent of vascular plants." 



Bower then proceeds to sketch the probable appear- 

 ance of Rhynia, whose external features and microscopic 

 structure have been marvellously well preserved : "Though 

 clearly a land-growing vascular plant, it had no leaves or 

 roots, but was composed of branched cylindrical stems. 

 Some of these ramified underground, and were attached 

 to the peaty soil by numerous root hairs, often grouped 

 on bosses of the outer cortex. Others grew upwards as 

 tapering aerial stems, which also bore bosses on their 

 surface. The lower of these bore root hairs ; others 

 appear to have produced lateral branches easily detached, 

 and serving for vegetative propagation. The cylindrical 

 stems consisted of a central core of conducting tissue, 

 covered by a cortex probably green, and invested by a 

 superficial epidermis with stomata, or breathing pores. 

 At the ends of stout stalks the plant bore cylindrical 

 sporangia, filled with spores of a type usual in vascular 

 plants. 



" In its leading characters of nutrition and propagation 

 Rhynia is clearly comparable to such types as ferns, club 

 mosses, and horsetails. Its peculiarity lies in the absence 

 of roots and leaves and in the apparently solitary distal 

 sporangia. In organisation it thus appears to take a 

 place intermediate between moss-like and fern-like plants. 

 This becomes more significant when its early occurrence 



