288 PROCEEDINGS OF THE AMERICAN ACADEMY. 



gave rise to bitumen, especially as there is every reason to believe that 

 the disproportion between animal and vegetable matter must have been 

 very much greater in the Paleozoic than in the present epoch. If the 

 Algae themselves gave rise to the bituminous matter, we would expect 

 to find them locally more or less completely transformed into this 

 substance. No cases of this kind exist so far as I am aware. 



Another strong argument against the algal hypothesis of the origin 

 of boghead coals is the fact that cannel coals, which are practically 

 identical with them in chemical composition, are recognized to be com- 

 posed predominantly of the spores of vascular cryptogams. Potonie ^^ 

 recognizes this identity of origin of cannel and boghead coals, since he 

 states that they are both " sapropelic " in their nature, that is, they 

 were both laid down in open quiet water and are both bituminous in 

 their chemical composition. It is not open to doubt that the bitumi- 

 nous character of cannel coal is mainly, if not entirely, due to the 

 enormous quantities of the remains of resinous spores of vascular 

 cryptogams which it contains. Boghead coals are like cannel coals in 

 their chemical composition, differing only in the more richly bituminous 

 characteristics, which they present. As has been pointed out in the 

 foregoing paragraphs, they are likewise notable for the greater propor- 

 tion of substance showing structure under the microscope. There 

 appears in fact to be a definite relation between the amount of struc- 

 tural elements and the proportion of bituminous matter found in such 

 coals. It appears clear from the description of the micro-organisms of 

 boghead coals, especially such of these as show them in a compara- 

 tively good condition of preservation, that the bodies in question 

 represent the spores (in most cases apparently the macrospores) of 

 vascular cryptogams. The greater concentration of the bituminous 

 substance in so-called boghead coals, moreover, is related to a much 

 scantier occurrence of such coals, which, as compared with cannels, 

 occur in beds of very restricted area. 



Apparently as a result of all the considerations brought forward in 

 the statement of the conclusions drawn from the present investigation, 

 we must regard the so-called boghead coals as essentially composed of 

 the remains of spores of vascular cryptogams and thus as closely 

 resembling cannels, which they in general differ from, only in the 

 greater concentration and larger size of the constituent spores. The 

 less abundant occurrence and more purely sporal composition of bog- 

 head coals is doubtless to be attributed to the nature of the component 



^^ Entstehung d. Stcinkohle u. Verwandter Bildungcn, Einschliesslich dea 

 Petroleums, p. 20. 



