.8,,. NOTES AND COMMENTS. 409 



is usual be considerably separated. Sometimes, as in Robinia 

 pseudacacia, the stipules are represented by thorns. 



VI. The presence of thorns in general. These often represent 

 small axillary branches, usually supplemented by normal leaf-buds 

 at their base, when the relative position and character of the thorns 

 and buds may be of value for distinguishing species. 



VII. The presence or absence of ridges on the bark. These are 

 usually related to the leaf-scars, being frequently decurrent from 

 them. The more or less rounded angles are also worth observing, 

 as in the frequently eight- to ten-angled stems of Samhiicus canadensis. 



Besides these more important characteristics furnished by the 

 annual growth of twigs, which " may be used in forming a sort of 

 artificial classification," there are others which are very useful in 

 distinguishing individual species. 



The colour of the bark of twigs being usually grey or brownish, 

 the constant presence of twigs with green bark, as in Sassafras 

 officinale, or shades of red or purple, becomes a valuable feature. The 

 character of the pith is at times useful. 



Other characteristics are very good, if present. For instance, 

 the form and character of next year's flowering buds, whether present 

 as naked catkins, or enclosed in more or less scaly buds. The 

 remains of last year's inflorescence may also help. The form of the 

 bark may be of service ; smooth, as in the beech, or peeling in sheets, 

 as in the birch, or, especially in older trees, showing characteristic 

 cracks. Finally, the habit of the shrub or tree is often very charac- 

 teristic, although the general aspect, resulting from the mode of branch- 

 ing, may be quite different in a young and an old tree, as in the elm. 



Although it must not be expected that these winter twigs, with 

 their scars and buds, will furnish better means of distinction than 

 the ordinary botanical ones, it is astonishing how successful they may 

 prove. The author suggests that a ready means of distinguishing 

 the ligneous plants would be a welcome addition to the curriculum 

 of subjects dealt with in the botanical institutions existing in many 

 States for the diffusion of knowledge of practical utility. 



Botanical Nomenclature. 



As the subject of nomenclature is now disturbing the minds of 

 botanists, the following letter, reprinted from the Botanical Gazette 

 of June, 1892, may be of interest. The last words of the well-known 

 American systematist will seem the more opportune, as it is in the 

 neo-American School of Botany that the disturbing influence has 

 largely arisen. The letter was dictated by Sereno Watson in his 

 last illness, and is as follows : 



" For some time I have had a desire to give expression to 

 my views upon botanical nomenclature. Under the circumstances 

 I must speak briefly and somewhat dogmatically. In my opinion 



