278 PROCEEDINGS OF THE AMERICAN ACADEMY. 



stituting the colony. Figure 4, Plate 1, shows a rather extensive field 

 under a low magnification. On the dark background formed by the 

 so-called fundamental substance of the coal may be distinguished va- 

 rious lighter areas, some of which figure as Algae, according to the 

 Eenaultian view, and others, even with the low magnification used, are 

 of such a rounded or angular contour that they obviously represent 

 the crushed remains of spores of the vascular cryptogams. The spongy 

 or mottled light bodies represent the supposititious Algae. As will be 

 shown later, the two kinds of appearances belong together, and only 

 the absence of thin serial sections could have preyented the distin- 

 guished French author, cited above, from recognizing this state of 

 affairs. Figure 5, Plate 1, shows part of the field reproduced in the 

 foregoing figure, on a considerably higher scale of magnification. 

 Figure 6, Plate 1, shows a little above the horizontal middle line 

 two bodies, which are obviously cryptogamous spores. The one on 

 the right partakes of the spongy or mottled appearance, presented by 

 the supposed Algae. Elsewhere, especially in the lower part of the 

 figure, are seen the remains of additional bodies, which take their place 

 among the reputed Algae of Renault. Figure 7, Plate 2, shows part of 

 the last figure more highly magnified to bring out more clearly the 

 structural features of the bodies represented in the foregoing figure. 

 In our next illustration. Figure 8, Plate 2, is represented another field 

 under moderate magnification. On the right is a light body represent- 

 ing a fragment of some broken-up plant, a kind of remains with which 

 both cannel and boghead coals abound. On the extreme left is seen a 

 cluster of structures representing a tetrad of spores. In the median re- 

 gion of the figure are several of Renault's putative Algae. Figure 9, 

 Plate 2, shows the tetrad from the left of the foregoing figure, somewhat 

 mroe highly magnified. It is now apparent that on the extreme right of 

 the tetrad one of the spores is cut through the back and the two angle- 

 wise plane surfaces. Another spore of the tetrad appears below and is 

 obviously of the same nature as Renault's Alga Pila kentuckijana. The 

 third visible member of the tetrad is less clearly seen on the upper side 

 and is not so obviously of the organization represented by the sup- 

 posed Algae. It will be well to defer the interpretation of the last 

 figure until a number of other illustrations of the imagined Algae of 

 Renault have been examined. Figure 10, Plate 2, represents a partic- 

 ularly striking view of a spongy or mottled mass, which at the same 

 time from its contour and angles, is obviously the spore of a vascular 

 cryptogam viewed from the plane of section through its angular inter- 

 nal face. The plane of section is so fortunate, in the compressed con- 

 dition of the spore, as to show at the same time part of the alveolar 



