PALEOBOTANY BERRY. 325 



sporophylls, alternating with foliage leaves, or more or less zonal in 

 their development, consist of a short axis terminating in a pair 

 of lanceolate lobes and bearing adaxially an elongated bilocular 

 slightly stalked synanginm, and producing but one kind of spores. 

 Both genera show a decided tendency toward repeated branching of 

 the sporophylls, a feature much emphasized by Thomas, Scott, and 

 Bower, but believed by the writer to be without significance. 

 Whether the sporophyll be regarded as morphologically a branch or 

 a leaf is disputed. 



Those who accept the latter view regard the Psilotales as sporan- 

 giophoric and closely related to the Sphenophyllales. Others consider 

 that the necessities of nutrition of large sporangia with many spores 

 resulted in the formation of sterile plates, such as occur in Isoetes 

 and in the sporangia of some of the Lepidodendrales, and regard the 

 bi- or trilocular sporangia of the Psilotales as septate unilocular spo- 

 rangia. The view that these masses of sterile tissue may represent 

 vestiges derived from sporangiophoric ancestry has not been suffi- 

 ciently emphasized and will be referred to in a subsequent para- 

 graph. Meanwhile, it may be said that the action of Scott and 

 others in separating the Psilotales from the Lepidophytes and group- 

 ing them with the Arihrophytes is greatly to be deprecated. The 

 fossil history of the Psilotales is unknown. Various fragmentary 

 specimens described as Psilotites are without value. Among the 

 doubtful forms that have been related to the Psilotales are the 

 Devonian genera Psilophyton, Dimeripteris and Pseudosporochus, 

 and the Permian genus Gomphostrobus. 



The order Lepidodendrales merits a more extended considera- 

 tion than has been accorded the preceding three orders. It consists 

 of three well-marked families very prominent in Paleozoic floras, 

 the Bothrodendraceae, Lepidodendraceae, and Sigillariaceae, to 

 which should possibly be added the Pleuromoiaceae for the recep- 

 tion of Triassic Sigillaria-like plants. Although herbaceous re- 

 mains are known, the vast majority of the Lepidodendrales were 

 arborescent and some of them reached a height of 100 feet or more. 

 The most ancient of these families, the Bothrodendraceae, unites in 

 many respects the features that later characterized the Sigillaraceae 

 on the one hand and the Lepidodendraceae on the other. The 

 Bothrodendraceae are especially characteristic of the Devonian and 

 Lower Carboniferous. They were cosmopolitan and their abundance 

 may be indicated by the fact that the so-called paper coal of Eussia 

 consists almost entirely of their flattened cuticles. A number of 

 generic types have been recognized, although our information re- 

 garding them is vague in a good many particulars. 

 136650°— 20 22 



