682 



NATURE 



[July 29, 1920 



structure. He distinguished several genera of 

 plants with branched cylindrical stems bearing 

 small thorn-like appendages, and some of them 

 distal sporangia. Many of his specimens were 

 referred to Fsilophyton princeps, and bore out 

 in the main the reconstruction of Dawson. Halle 

 was able to confirm the existence of a central 

 vascular strand in Psilophyton, consisting of 

 tracheides, a fact which ranks it with certainty 

 among vascular plants of the land. But the most 

 distinctive novelty which Halle discovered in the 

 Roragen beds was a fossil which he called Sporo- 

 gonites. It consisted of a simple stalk bearing 

 a terminal capsule. From its form, and the char- 

 acter of its contents, he held it to be a sporo- 

 gonium comparable with that of the Bryophytes ; 

 but a generalised type, not referable to any exist- 



FiG. I. — Vertical section through the protocoriji of R/tym'a Ligm'eri 



ing group of them. An alternative suggestion 

 was that Sporogonites may represent only the 

 upper part of a more highly developed sporo- 

 phyte, perhaps on the line of descent of the 

 Pteridophytes. Thus the presence of Sporogonites 

 does not actually prove the existence of Bryo- 

 phytes as we now know them in the early 

 Devonian rocks. But nevertheless it has a 

 peculiar interest. Hitherto there has been no 

 certain record of the existence of any moss-like 

 type in the Palaeozoic period. The demonstration 

 of so moss-like a sporangium as Sporogonites is 

 certainly the most thrilling of the facts brought 

 forward by Dr. Halle. 



In 1913, three years before Dr. Halle's publica- 

 tion of these discoveries at Roragen, the first of 

 NO. 2648, VOL. 105] 



the new observations of early Devonian plants 

 in Scotland was recorded. Dr. Mackie, of Elgin, 

 found at Rhynie, in Aberdeenshire, certain iso- 

 lated blocks of chert containing plant remains. 

 A little later the source of these blocks was 

 traced to a bed of chert, older than the Upper 

 Devonian, fourid in situ by the Scottish Geo- 

 logical Survey. Its origin appears to have been 

 this. An exposed land-surface existed there in 

 Middle or Lower Devonian time, subject to in- 

 tervals of inundation. It became periodically 

 covered by vegetation. By decay of its stems and 

 underground parts a bed of peat would be formed. 

 The peat was then flooded, and loose sand de- 

 posited over it. Again the vegetation was re- 

 peated, and so successive bands were formed to 

 some 8 ft. in thickrfess.' Then followed water 

 with siHca in solu- 

 tion, supplied from 

 some fumarole or 

 geyser. The peat- 

 bed was thus sealed 

 up, and the plants 

 preserved with as- 

 tonishing perfection. 

 From this bed of 

 chert four distinct 

 vascular plants have 

 been recognised, and 

 described in the 

 minutest detail by 

 Dr- Kidston and 

 Prof. Lang. They 

 are all essentially 

 similar in type, 

 though sufficiently 

 different to be placed 

 in three genera, 

 named respectively 

 Rhynia (two species), 

 Hornea, and Astero- 

 xylon. 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 Psilo- 

 phyton 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 



