L38 Dr. F. 0. Bower [April 30, 



Professor Lang. They are all essentially similar in type, though 

 sufficiently different to be placed in three genera, named respectively 

 Rhynia (two species). Hornea and Asteroxylon. Rhynia and Hornea 

 are leafless and rootless, while Asteroxylon is also rootless, but it 

 bears leaves of a simple type. The plants thus clearly indicate a 

 primitive state prevalent at that period. They conform in general 

 features to the type of Psilophyton as described by Dawson, and as 

 recognised in greater detail by Halle. But here in the Rhynie chert 

 the structural details are so well preserved that these earliest of all 

 known vascular plants can be examined and described almost as well 

 as any modern living plants. Some have even been found standing 

 erect as in life. Through untold ages, like the legendary Knights of 

 the Round Table, they have thus awaited the revivifying touch of 

 Modern Science. 



Of the four plants so far described from the Rhynie chert, 

 Hornea Lignieri is relatively simple. From a distended and lobed 

 protocormous base rose the stems, which bifurcated. These bore 

 distal sporangia, which represent their transformed tips. Sometimes 

 the sporangia were themselves forked. The protocorm was bedded 

 in the peat, and parenchymatous, with many rhizoids (Fig. 1). The 

 cylindrical stems stood upright from it, and were about 2 mm. in 

 diameter. They were traversed by a simple stele with a solid core of 

 tracheides, surrounded by phloem. The stele forked at the dicho- 

 tomies of the stem, but stopped short at the base of the sterile 

 columella, which ran upwards into the flat-topped, and apparently 

 inclehiscent, sporangium. The latter appears as a transformation of 

 the end of the stalk, which is simply an ordinary branch of the 

 plant. The spores are tetrahedal, as they are in all of these plants 

 of the chert. The general aspect of Hornea is such as to provoke 

 comparison with the Bryophytes, notwithstanding certain strongly 

 divergent characters. This may have some real significance in view 

 of its small size, and relatively simple structure. 



Rhynia major is larger and better preserved, but still it also is 

 structurally simple (Fig. 2). It had a less distended rhizome, from 

 which the robust cylindrical stems arose. These consisted, as in 

 Hornea, of a central stele with solid xylem-core and investing 

 phloem, surrounded by a massive cortex, of which the inner region 

 appears to have been photosynthetic. Outside was a well-marked 

 epidermis with stomata (Fig. 3). These and the vascular tissue 

 prove the aerial habit of the plant. The stems ended in solitary 

 massive sporangia, as much as 12 mm. in length, without a columella, 

 and filled with tetrahedal spores (Fig. 4). 



Neither of the species described bore any appendages on their 

 stems. Rhynia Gwynne-Vaughani, though smaller than R. major, 

 shows a feature of morphological advance towards something in the 

 nature of appendages. The upright stems bifurcate as before, 

 bearing distal sporangia similar to, but smaller than, those of R. major. 



