210 The Palaeontological Record, II. Plants 



Selaginellae takes place by free spermatozoa, and in the Coniferae 

 by a pollen-tube, in the interior of which spermatozoa are probably 

 formed"— a remarkable instance of prescience, for though sperma- 

 tozoids have not been found in the Conifers proper, they were 

 demonstrated in the allied groups Cycadaceae and Ginkgo, in 1896, 

 by the Japanese botanists Ikeno and Hirase. A new link was thus 

 established between the Gymnosperms and the Cryptogams. 



It remained uncertain, however, from which line of Cryptogams 

 the gymnospermous Seed-plants had sprung. The great point of 

 morphological comparison was the presence of two kinds of spore, 

 and this was known to occur in the recent Lycopods and Water-ferns 

 (Rhizocarpeae) and was also found in fossil representatives of the 

 third phylum, that of the Horsetails. As a matter of fact all the 

 three great Cryptogamic classes have found champions to maintain 

 their claim to the ancestry of the Seed-plants, and in every case 

 fossil evidence was called in. For a long time the Lycopods were 

 the favourites, while the Ferns found the least support. The writer 

 remembers, however, in the year 1881, hearing the late Prof. Sachs 

 maintain, in a lecture to his class, that the descent of the Cycads 

 could be traced, not merely from Ferns, but from a definite family of 

 Ferns, the Marattiaceae, a view which, though in a somewhat crude 

 form, anticipated more modern ideas. 



Williamson appears to have been the first to recognise the 

 presence, in the Carboniferous flora, of plants combining the charac- 

 ters of Ferns and Cycads 1 . This conclusion was first reached in the 

 case of the genera Heterangium and Lyginodendron, plants, which 

 with a wholly fern-like habit, were found to unite an anatomical 

 structure holding the balance between that of Ferns and Cycads, 

 Heterangium inclining more to the former and Lyginodendron to the 

 latter. Later researches placed Williamson's original suggestion on 

 a firmer basis, and clearly proved the intermediate nature of these 

 genera, and of a number of others, so far as their vegetative organs 

 were concerned. This stage in our knowledge was marked by the 

 institution of the class Cycadofilices by Potonie^ in 1897. 



Nothing, however, was known of the organs of reproduction of 

 the Cycadofilices, until F. W. Oliver, in 1903, identified a fossil 

 seed, Lagenostoma Lomaxi, as belonging to Lyginodendron, the 

 identification depending, in the first instance, on the recognition 

 of an identical form of gland, of very characteristic structure, on the 

 vegetative organs of Lyginodendron and on the cupule enveloping 

 the seed. This evidence was supported by the discovery of a close 

 anatomical agreement in other respects, as well as by constant 



1 See especially his " Organisation of the Fossil Plants of the Coal-Measures," Part xm. 

 Phil. Trans. Royal Soc. 1887, b. p. 299. 



