484 PAL^OBOTANY. 



floating plants, and they occur in both the Devonian and 

 Carboniferous formations. 



Fig. ^.AsterophyUitesfoliosus. Coal-measures. (After Lindley and Hutton.) 



The fossils known as Pinnularics are slender stem-like bodies, 

 with a smooth or striate surface, producing at right angles long 

 slender branchlets. The genus Pinnularia is regarded by 

 Dawson as being founded upon the roots of other plants, such 

 as Asterophyllites or Catamites. 



Lastly, we find in the Devonian Rocks the little fruits 

 known as Cardiocarpon and Trigonocarpon, which are so abun- 

 dant in the Coal-measures. The Cardiocarpa appear mostly 

 to have been winged achenes or " samaras ; " but it is not 

 altogether certain by what plants they were produced. It is 

 now known, however, that the so-called Antholithes consists of 

 a spike, bearing Cardiocarpa protected by bracts ; and there is 

 a considerable probability that they were produced by Sigil- 

 larioid trees. Trigonocarpon (fig. 383) 

 comprises nut-like fruits, often of 

 considerable size, and commonly 

 three- or six- angled. The exterior of 

 the fruit was probably fleshy, and well- 

 preserved specimens show the integu- 

 ments, and the internal cavity at one 

 time filled by the albumen and em- 

 ' bryo. Trigonocarpon is probably the 

 fruit of a Conifer, and it shows a de- 

 cided resemblance to the solitary fruit of the existing Taxoid 

 genus, Salisburia. Possibly, however, Dr Dawson is correct 

 in his conjecture that most of the Trigonocarpa belonged really 

 to Sigillarioid plants. 



