THALLOPHYTES, BRYINAE. 47 



between Saporta l and Delgado 2 , as the chief maintainers of the algal 

 nature of the objects in question, and Nathorst 3 as representing the oppo- 

 site opinion. So far as I may presume to judge in this matter, I should say 

 that, as usually happens in such cases, both sides go too far. Nathorst, 

 though he allows that there are some fossil Algae, makes the presence of a 

 rind of coal the ultimate criterion, and roundly denies the algal nature of 

 any form where that is not found. It appears from the remarks in the 

 introductory chapter to the present work, that this cannot be admitted. We 

 know that the coal may entirely disappear in the course of time from 

 remains that are undoubtedly organic, if they are deposited in a porous 

 rock. Moreover, Nathorst refuses to allow that any of the remains 

 which occur in half-relief on the surface of slabs of stone belong to the 

 vegetable kingdom. Saporta 4 , as has been already stated in the Intro- 

 duction, attacks this doctrine on good grounds and with more than usual 

 earnestness. 



The whole question in dispute is not one in which the botanist is 

 greatly interested, for even remains, which being provided with strips of 

 coal are allowed by both sides to be Algae, such for example as many 

 specimens from the Eocene beds of Mte Bolca and from the Upper 

 Oligocene (Aquitanian) beds of Sotzka and Radoboj, are of no value to 

 him, except in the few cases in which the external form is so well marked 

 that he can venture to connect them with living forms, as is the case, for 

 example, with the Cystoseiritae of Radoboj. There may possibly be remains 

 of true Algae among specimens obtained from other formations, but no 

 proof of this can be produced, and we cannot therefore at present attempt 

 more exact determination of the family to which they belong. 



On the other hand, it has been shown in many cases that supposed 

 remains of Algae are of a totally different nature. Of this we have a 

 number of striking instances, for which we are chiefly indebted to Nathorst, 

 quite apart from mistakes such as that made by Saporta 5 , who confounded 

 flattened oyster-shells with Algae, as in the case of Conchyophycus Mar- 

 cignyanus, Sap. 6 placed with Cutleria and Zonaria ; but he has since 

 acknowledged the real nature of this object 7 . It may be remarked in 

 passing that Nathorst gives a complete list of the older literature of the 

 subject, which may be referred to for the following statements. Resting 

 on the observations of several of the older writers, Ernmons, Hancock, 

 Dawson and others, who had explained certain of the supposed Algae as 

 imprints of the tracks of animals, Nathorst tried the experiment of obtaining 

 tracks of the kind on prepared ground and then taking casts of them in 

 plaster of Paris. A variety of imprints were thus procured in half-relief, 



1 de Saporta (1), (12) and (13). 2 Delgado (1). 3 Nathorst (1). * de Saporta (1). 



5 de Saporta (4). de Saporta (4), vol. i, p. 150 ; t. 1 1. 7 de Saporta (4), vol. i, p. 469. 



