DIOECIA— DIANDRIA. Salix. 16j 



tiire of species, or the production of new, or hybrid ones, 

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

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

 tions in the sliapes and sizes of leaves, and their stipulas, 

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

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

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

 Willows should be p.articuhn-ly stuched at three different 

 seasons; die flowering time, die early part of summer, 

 when the young shoots, with their stiindas and expand- 

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

 leaves are come to their full size. No botanist therefore 

 can be comj^etent to form an opinion about them, unless 

 he resides among tlie 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 tiiis 

 department of Botany, and indeed in every other, cannot 

 be too stricdy enforced, ^^^e should study a species 

 before we decide on its characters, and not lay down 

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

 ferences of simple or compound, entire, serrated or jagged 

 leaves, the presence or absence of 5/?/w/«5, though usually 

 so essential and decisive, make no specific distinction at 

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

 specific characters, in others some diflerent part. The 

 distinctions of Willows are frequently so very nice, that 

 the greatest observation and experience only can stamp 

 them with due audiority. 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 hojicd that mv excel- 

 lent friend Dr. Hooker would have given ^Ir. Crowe and 

 myself credit for some accuracy of observation, and not 

 have set almost all our labours at nought, witiiout some 

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

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

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

 should dcpieciate him in the opinion of persons who do 

 not know him so well as 1 do. Satislietl widi a careful 

 revision of the subject, and niih correcting myself 

 wherever I could find occasion, 1 leave to others the un- 

 grateful task of criticism. The errors of sonic, other- 



