46 THALLOPHYTES, BRYINAE. 



to the Lower Silurian, which have been described under an abundance of 

 generic names ; but they have virtually no interest for the botanist, because 

 there is no immediate possibility of profitable comparison with known algal 

 types. We may perhaps be able at some future time to pick out a type 

 here and there out of this hopeless chaos, but it is scarcely possible that we 

 shall ever attain to a better position as regards the remainder. We must 

 necessarily be always dependent on characters derived from external form, 

 and these in the case of the Algae prove only too little ; we can scarcely 

 hope to penetrate to the inner structure of the fructification, which can 

 alone determine the affinity. And, to meet an objection which may be 

 expected from the palaeontologists, I will add at once that I should not 

 hesitate to say the same of the Coniferae, for instance, if we had nothing 

 left of them but the impressions of the leaves ; but there we are better off, 

 for cones, wood, and fragments showing anatomical structure have been 

 preserved as so many points of support for the conclusions, by which we can 

 be continually testing the degree of probability to be assigned to new con- 

 quests. What mistakes may be made without the aid of such objects is 

 shown by the number of impressions of Conifers, which are explained by 

 older authors, by Brongniart for example, as Zonarites digitatus, various 

 Caulerpitae and other Algae. 



This problematical character of the remains could not well escape the 

 attention even of the earlier observers, who soon accustomed themselves to 

 describe everything as an Alga which could not be disposed of elsewhere. 

 Hall's l remark is much to the point : ' It has been the habit to refer to 

 vegetable origin all those fossil bodies of the older strata which have in 

 their general aspect, their habit or mode of growth some similarity to plants, 

 and in which no organic structure can be detected beyond sometimes the 

 external markings.' That so large a proportion of 'Algae' were brought to 

 light from the oldest formations was entirely due to the fact, that there was 

 a more eager search for organic remains there than elsewhere to meet the 

 requirements of geological investigation. In recent times the later forma- 

 tions also have been diligently examined for the same purpose ; but in the 

 Silurian and Devonian deposits every bit of raised surface however shapeless 

 was named in this way, as may be seen from the figures of the genus 

 Eophyton, Torell, to be found in Saporta 2 . From such an extension of the 

 idea of a fossil Alga a speedy reaction was inevitable, and attempts were 

 made to show that many of the objects described as Algae were casts of 

 the tracks of animals, like the well-known impressions of Chirotherium from 

 the Bunter Sandstein, and that others again were merely of inorganic origin. 

 This divergence of views has recently given rise to a lively discussion 



Hall (1), vol. ii, p. 18. " de Saporta ^1), p. 6s,, and '3), p. 82. 



