n6 



VASCULAR CRYPTOGAMS 



central 'vascular' cylinder can be detected, consisting of scalariform 

 tracheides. There is distinct evidence of a secondary growth in thick- 

 ness. The branching was always dichotomous. The leaves were very 

 similar to those of Lycopodium, and were penetrated by a single 

 -vascular' bundle. 



The fructifications known as Lepidostrobus are cone-like structures, 

 not unlike fir-cones in appearance, consisting of densely packed sporo- 

 phylls. On the upper side of each leaf is a single sporange, often of 

 considerable size. The cones themselves vary in size from that of a 

 hazel-nut to one and a half feet in length. It is seldom that the remains 

 are in a sufficiently perfect condition for the structure of the spores to 



A 



I 



FIG. 88. A, transverse section of cone of Lepidostrobus Browmi Schimp. ; B, longitudinal section 

 (after R. Brown) ; C. diagrammatic longitudinal section of portion of cone of L. ornati4s Hook. 

 (after Hooker) ; D, upper surface of sporophyll {Lepidophylhun). (All from Solms-Laubach.) 



be made out with certainty ; but in several examples both kinds occur. 

 Where one kind only has at present been detected, it is, in most cases, 

 the microspore, the megaspores being probably in the lower part of the 

 fructification, which has not been preserved or examined. In the mega- 

 s.pores the exospore has three ridges ; there are numerous spores in each 

 sporange. The microspores of L. dabadianus (Schpr.) are connected 

 together in groups of four ; while in L. Brownei (Schpr.) they are in threes. 

 More or less nearly allied to Lepidodendron are a number of other 

 arborescent genera, among the more striking of which are Ulodendron 

 (Stbg.), Bothrodendron (L. and H.), and Lepidophloios (Stbg.), all from 

 the coal measures. 



