PRESENTATION OF TABLET 67 



mere amateur. They incidentally reveal that his beliefs 

 on various questions were in accord with those now 

 held rather than with those prevalent when he expressed 

 them. For example, in his Manual of Botany., issued 

 in 1840, he says "There is nothing absolutely certain 

 as to species, much less as to the groups into which they 

 are disposed, as genera, families, orders, tribes, and the 

 like. We merely agree to consider as species individual 

 plants which closely resemble each other in the structure 

 and form of their organs. Such species, however, often 

 pass into each other by gradations, which render it 

 impossible to draw a line of demarcation, and thus all 

 species are more or less arbitrary. We know from 

 observation that all assumed species undergo changes 

 from climate, cultivation, and other influences ; and 

 individuals exhibiting remarkable alterations we call 

 collectively varieties ; but variety is a still more vague 

 idea than species." He edited in one volume a reduced 

 form of Withering's Botany. That this service to 

 British botany was considerable was proved by numerous 

 editions of the book in this form, each of those issued 

 before his death being revised by him. His interest in 

 botany and geology are further shown by papers pub- 

 lished in scientific journals, and by one of his latest 

 works, the Natural History of Deeside. But zoology 

 was his favourite science ; and his books and papers on 

 branches of zoology are many and valuable. All come 

 fresh to the student as the work of a man that tells of 

 what he saw in language remarkable in style as well as 

 in accuracy. 



