270 SCIENCE PROGRESS. 



Primary Xylem proceeding from above downwards, is 

 incapable of explaining the facts recorded in the preceding 

 pages. Hence, that explanation appears more likely to be 

 found in some modification of the views of Graf Solms." 

 He goes on to point out, with perfect justice, that certain 

 difficulties still remain. 



It requires a very noble spirit of self-abnegation for a 

 scientific man, at the age of seventy-eight, thus to sacrifice 

 to the cause of truth opinions which he had upheld for so 

 long. 



We have only touched on certain parts of Williamson's 

 work, and have left an immense number of his investiga- 

 tions altogether unnoticed. It seemed best however to 

 make a selection, and to choose as illustrations the four 

 great types of Vascular Cryptogams on which his most 

 striking results were obtained. 



Some apology is perhaps due for the very slight 

 reference which has been made to the work of other 

 palaeobotanists. This article relates merely to Williamson's 

 own researches, and it would have been impossible, without 

 extending it beyond all reasonable limits, to include any 

 adequate account of the share of other observers in building 

 up the present fabric of our knowledge. 



We cannot conclude this sketch of Williamson's work 

 on carboniferous plants without some allusion to his remark- 

 able powers as a draughtsman — powers which most of us 

 must be content to admire without emulating. Almost all 

 the illustrations to his numerous papers, and in fact all 

 those which relate to anatomical structure, are by his own 

 hand. It is hard to understand how so busy a man can 

 have found the mere time for such minute and detailed 

 labour, but the character of the work (to which full justice 

 is not always done in the published reproductions) bears 

 witness, not only to his marvellous industry, but to rare 

 artistic skill. 



BIBLIOGRAPHY. 



(1-19) WILLIAMSON. On the Organisation of the Fossil Plants of 

 the Coal-Measures, parts i.-xix. Philosophical Transactions 

 of the Royal Society, 1 871-1893. 



