Ixxxii PROCEEDINGS OF THE GEOLOGICAL SOCIETY, [vol. lxxix, 



ask, may it, perhaps, have originally lived in the sea, surviving the 

 ordeal of translation to a land-habitat without any substantial 

 modification of its anatomical features ? 



It would lead us too deeply into botanical technicalities to 

 include in a general summary an adequate review of the older fossil 

 records of tbat family of Algae known as the Siphonese Verticillatse, 

 green seaweeds which exist in the warmer seas to-day, and are 

 recorded as fossils from Silurian strata upwards. The family, with 

 especial reference to the extinct types, has recently received a com- 

 prehensive and able treatment at the hands of Dr. Julius Pia, of 

 Vienna. This author speaks of the Siphonese Verticillatse as a very 

 homogeneous and natural assemblage of Algae, producing in the 

 course of their long history successive series of new forms, per- 

 sistent in the retention of family characters, but rapidly changing 

 in the manifold expression of these characters. Palseobotanical 

 research brings to light many examples of fluctuations within the 

 range of a genus or a family ; but it fails, I venture to think, to 

 demonstrate lateral connexions between families, classes, and 

 groups. Genealogical trees of the comprehensive type have had 

 their day : single lines of development are clearly discerned, 

 stretching, it may be, to almost infinitely remote ages. Our failure 

 to discover, either the meeting-places of these lines, or connexions 

 between them, may be consistent with the course of evolution, and 

 not merely a consequence of the imperfection of the geological 

 record. 



In 1869 H. A. Nicholson described some obscure fossils from 

 the Skiddaw Slates as vegetable impressions : two of them, referred 

 to Hall's genus Buthotrepliis. were believed to indicate land-plants. 

 Dawson substituted the generic name Protannularia in his 

 account of similar fossils from the Devonian of Canada. In both 

 the English and the Canadian specimens the radially-disposed 

 carbonaceous markings on the rock bear a superficial resem- 

 blance to the leaf-whorls of the well-known genus Annularia. 

 The late Dr. E. A. N. Arber, while fully admitting the doubtful 

 character of the evidence, expressed the opinion that ' it is quite 

 possible that Protannularia radiata may be the oldest, in a geo- 

 logical sense, British land-plant '. An examination of Nicholson's 

 type-specimens in the Sedgwick Museum convinces me that any 

 satisfactory determination of their affinity is impossible. 



