part 2] ANNIVERSARY ADDRESS OF THE PRESIDENT. lxxxv 



The Earliest Land-Plants. 



We will pass now to consider some of the earliest examples of 

 fossil plants that may reasonably he regarded as the remains of a 

 terrestrial vegetation. Reference has already been made to certain 

 obscure impressions described by Nicholson from the Skiddaw 

 Slates, which, although too imperfect to determine with any degree 

 of confidence, may, as Arber suggested, be the oldest-known relics 

 of a land flora. The records from Silurian rocks are very meagre ; 

 but, meagre as they are, they give some weight to the suspicion 

 that precursors of some of the succeeding Devonian types had 

 already established themselves on the land. In the British 

 Museum (Natural History) there are a few specimens of small 

 dichotomously branched axes, with crowded, spirally disposed 

 appendages, from the Lower Ludlow Beds of Staffordshire, which 

 bear a close resemblance to a fossil described by T. G. Halle from 

 rocks of the same age in the island of Gothland. The precise 

 nature of the appendages is not clear: those of the English 

 specimens were probably not true leaves, but slender branches. 

 Halle, in naming the Gothland species Psilophyton (?) lieclei, 

 tentatively connects it with a genus which is characteristic of 

 older Devonian floras, and was said by Dawson to occur also in 

 Upper Silurian strata in Canada. While it is impossible to 

 establish a definite relationship between Silurian fragments and 

 the Devonian land-plant Psilopliyton, they certainly suggest a 

 possible alliance. 



The small discs known as ParTca decipiens, though most abun- 

 dant in Lower Old Red Sandstone rocks in Scotland, may be 

 briefly considered here, as they are recorded also from Upper 

 Silurian localities in England. We are indebted to the late 

 Mr. Archibald Don and to Dr. G. Hickling for the most complete 

 account of this problematical genus. The discs consist of spherical 

 masses of spores enclosed in thin tissue bounded above and below 

 by a covering layer of cells. In a note published in 1921 

 Mi 1 . W. N. Edwards described two specimens in the British Museum 

 which, he believes, afford some evidence of the attachment of the 

 discs to a stalk : the evidence, though not convincing, is in agree- 

 ment with an opinion expressed in 1898 that Parlca was originally 

 attached to a supporting axis. The systematic position of the 

 genus has not been definitely determined : Don & Hickling 



