DIOECIA— DIANDRIA. Salix. 1G5 



ture of species, or the production of new, orliybrid ones, 

 of which, no more than of any change in established spe- 

 cies, I have never met with an instance. Strange altera- 

 tions in the shapes and sizes of leaves, and the'iv s//j)i//aSf 

 have indeed been seen, on young ratlical shoots, from a 

 tree, or bush, that has been felled ; but not more than 

 usually happens in Poplars, Limes, Elms, and others. 

 Willows should be particularly studied at three different 

 seasons; the flowerhig time, the early part of summer, 

 when the young shoots, with their stipulas and expand- 

 ing foliage, are to be observed ; and finally when the 

 leaves are come to their full size. No botanist therefore 

 can be competent to form an opinion about them, unless 

 he resides among the wild ones, for several seasons, or 

 continually observes them in a garden. No hasty tra- 

 veller over a country, no collector of dried specimens, or 

 compiler of descriptions, can judge of their characters, or 

 essential differences. One principle above all, in this 

 department of Botany, and indeed in every other, cannot 

 be too strictly enforced. We should study a species 

 before we decide on its characters, and not la}"^ down 

 rules of definition beforehand. In many plants, the dif- 

 ferences of simple or compound, entire, serrated or jagged 

 leaves, the presence or absence o? stijmlas, though usually 

 so essential and decisive, make no specific distinction at 

 all. In some tribes, or genera, one part affords the best 

 specific characters, in others some different part. The 

 distinctions of Willows are frequently so very nice, that 

 the greatest observation and experience only can stamp 

 them with due authority. Yet persons to whom their 

 qualities and uses are of the last importance, might hold 

 a botanist very cheap, who could not help them to know 

 one from another. I should have hoped that my excel- 

 lent friend Dr. Hooker would have given Mr. Crowe and 

 myself credit for some accuracy of observation, and not 

 have set almost all our labours at nought, without some 

 practical knowledge, at least, of his OAvn. I am well 

 convinced that he meant to be right, and should be truly 

 sorry that his decisions, or his style of expressing them, 

 should depreciate him in the opinion of persons who do 

 not know him so well as I do. Satisfied with a careful 

 revision of the subject, and with correcting myself 

 wherever I could find occasion, I leave to others the un- 

 grateful task of criticism. The errors of some, oilier-^ 



