CHAP, v Palacobotany 1 860- i goo 147 



established by the more thorough examination of several 

 types which on their first discovery had been very difficult 

 to classify. The first of these was Lyginodendron, a fossil 

 whose stem was discovered by Binney in 1866. It was 

 described by Williamson in 1873, and more fully in later 

 years, but the results of a very much more complete 

 examination were published by Williamson and Scott in 

 1895. The disposition of its tissues recalled Cycadean 

 structure, which was confirmed by Scott's investigation in 

 1897 of the anatomical characters presented by the peduncle 

 of the cones of Stangeria and other recent genera. 



Recent investigations have brought to light that the 

 fossil described in 1876 by Williamson, under the name of 

 Kaloxylon, was the root of Lyginodendron, that Rachio- 

 pteris aspera was its petiole, which bore leaves that were 

 described under the name of Sphenopteris Honinghausii. 

 The whole of the vegetative part of the plant has con- 

 sequently been reconstructed. 



Another plant, showing much in common with Lygino- 

 dendron was Heterangium, which \vas first found by Corda 

 in 1845 ; a species of the genus was described by Williamson 

 in 1873, and another one in 1887. Heterangium, together 

 with Lyginodendron, was dealt with by Williamson and 

 Scott in their memoir of 1895. 



The association of another type with these was the out- 

 come principally of Renault's work. In 1874 he made 

 a careful study of the petioles of the so-called ferns Neuro- 

 pteris and Alethopteris, which he named Myelopteris. It 

 has already been mentioned that in 1883 Stur claimed that 

 these were not properly to be considered Ferns, as no 

 fructification of fern-like character had been detected among 

 the numerous specimens that had been examined. In the 

 same year Renault showed that they had petioles of the 

 type described by Brongniart under the name of Myeloxy- 

 lon. In the meantime, in 1880, Weber and Stenzel proved 



K 2 



