XXXI 



Perhaps the greatest result was his demonstration, after a contro- 

 versy extending over a quarter of a century, that the Sigillarian and 

 Calamarian trees of the Carboniferous period were Cryptogams. To 

 use his own words : " The fight was always the same : Was Brong- 

 niart right or wrong, when he uttered his dogma, that if the stem of 

 a fossil plant contained a secondary growth of wood, the product of 

 a cambium layer, it could not possibly belong to the cryptogamic 

 division of the vegetable kingdom?" Williamson ultimately suc- 

 ceeded in convincing his opponents, including almost all the members 

 even of the French school, that the plants in question are nothing 

 but highly organised Cryptogams, their secondary growth being 

 mainly an adaptation to arborescent habit, and by no means an indi- 

 catioln of Phanerogamic affinities. Tn this controversy Williamson 

 had two sets of opponents ; namely, those who followed Brongniart 

 in regarding plants with secondary growth as necessarily phanero- 

 gamic, and those who, while recognising the cryptogamic nature 

 of the plants under discussion, denied or minimised the secondary 

 growth itself. Williamson, in spite of occasional mistakes in detail, 

 was ultimately victorious on both issues; there is to-day, not the 

 slightest doubt that most Palaaozoic Cryptogams formed, by means 

 of cambium, secondary tissues essentially similar to those of Dicotyle- 

 dons or G-ymnosperms, and that these plants were none the less as 

 truly cryptogamic as their less highly organised representatives at 

 the present day. 



But, apart from this controversy, upon which it is superfluous to 

 dwell longer, Williamson advanced our knowledge of the ancient 

 plants in many directions, especially as regards the Sphenophylleaa, 

 of which he discovered the first fructifications showing structure ; 

 the fructifications of Calamarieaa and Lepidodendreoe ; the various 

 types of structure among the fossil Lycopods ; the existence of a 

 group on the frontier of Ferns and Cycads, &c. He made mistakes, 

 as all do, who carry out extensive investigations in a new field, but 

 he corrected most of them himself, and they in no way afiect the per- 

 manent value of his great work in laying the secure foundations of 

 scientific palaeozoic botany. 



Williamson's remarkable skill as a draughtsman added greatly to 

 the value of his memoirs, which are illustrated almost wholly by his 

 own hand. He was by nature an artist, and, in addition to his scien- 

 tific drawings, painted many pleasing landscapes in water-colours 

 during his leisure hours. 



Williamson was an all-round naturalist of a type now unhappily 

 all but extinct. He made his mark as a distinguished original 

 the obituary notice by Solms-Laubacli, in ' Nature ' for September 5, 1895 ; and 

 D. H. Scott, " Williamson's Eesearcb.es on the Carboniferous Flora," ' Science 

 Progress,' December, 1895. 



