4 '44 SKETCH OF PALEOBOTANY. 



ever imperfectly sucli a flora was represented in the collections, this re- 

 lation would theoretically hold, and thus the imperfection of the geolog- 

 ical record would be eliminated so long as it was only contemplated 

 from this relative stand-point. And although it is not true that all 

 kinds of plants stand an equal chance of preservation, still the classi- 

 fication of plants according to their adaptability to preservation is 

 wholly different from their systematic botanical classification and trav- 

 erses the latter in such a manner as rarelyto coincide with its bound- 

 ary lines or to exclude any entire group from the possibility of being rep- 

 resented in the fossil state. Nevertheless, such omissions, or at least very 

 disproportionate representations, will occur and must be allowed for. 

 Tlie theory also fails where a flora is only very meagerly represented, 

 and the smaller the representation the less applicable the principle. This 

 accounts for certain great irregularities in the diagram, which are great- 

 est in the least adequately represented formations. Such defects will 

 be readily rectified by the intelligent student of the diagram, and it was 

 thought better to leave this to his judgment than to attempt to overcome 

 the defects by an arbitrary reduction of irregularities. The numerical 

 table will aid in making the proper allowance in each case by indicat 

 ing, as the diagram cannot do, the poorly-represented horizons. Upon 

 the whole this diagram may be regarded as trustworthy in intelligent 

 hands and as fairly indicating all that is claimed for it. 



That vegetable life should have preceded animal life is a fair deduction 

 from all that we know of these two kingdoms of nature, and, not to 

 speak of the much-disputed Eozoon Canadense of Canadian so-called 

 Azoic rock, we at least have Oldhamia in the Cambrian, whose organic 

 character is quite generally admitted. This and other facts give weight 

 to the view that the dark carbonaceous substance found in the Lauren- 

 tian has been the result of accumulated vegetable matter of marine ori- 

 gin, but too frail in structure to admit of preservation in any other form. 

 Graphite, too, which is a pure form of carbon, and thus almost demon- 

 strates vegetable origin, is found below the Silurian. But, dismissing 

 these speculations and admitting the somewhat doubtful vegetable 

 character of Oldhamia, we actually have organized plants, marine algae, 

 preserved in the Lower Silurian and even at its base. Such are Bilo- 

 bites rugosa, Chondrites antiquus, and Sphaerococcites Scharyanus. The 

 Cellular Cryptogams are thus fairly introduced at points lower than 

 that of the appearance of any higher type of vegetation, and by the close 

 of the Silurian fifty species had made their appearance, constituting 

 85 per cent of all the life of that epoch as thus far found. ISTot only in 

 this case, but all through the series, the order in which these great 

 types of vegetation are here drawn up agrees substantially with that of 

 their appearance on the globe, as shown by actual specimens collected 

 and determined. If the system of classification had been based exclu- 

 sively upon paleontological data, there would be no force in this, but, as 

 I have shown, it is in large measure that of botanists proper who never 



