120 On the requisites necessary 



in the elaboration of the genus. So clear is my opinion upon this 

 point, that, if it had been possible to prove the four species to which 

 I have alluded to be themselves physiologically distinct, I should at 

 once have reduced all the others to their original places ; but as it 

 is in the highest degree uncertain whether R. fruticosus, corylifo- 

 lius and ccesius are not as much varieties of each other, as those 

 which it would be necessary to reject, I have thought it bet- 

 ter to steer a middle course, until some proof shall have been ob- 

 tained either one way or the other. Accordingly, I have taken R. 

 fruticosus, corylifolius, ccesius and suberectus as heads of sections, 

 and I have assigned them characters which may be considered either 

 as sectional or specific, according as the evidence may ultimately 

 preponderate ; and I have arranged as species under them those 

 forms which are the best marked and the most clearly distinguish- 

 able. This will bring the genus Rubus somewhat into the situation 

 of Rosa ; in which, I fear, we must be satisfied with leaving it for 

 the present." 



We have dwelt somewhat longer upon this topic than to many 

 may seem advisable, but we feel so thoroughly persuaded of the very 

 great importance of some exertions being made for the purpose of 

 obtaining a better criterion for the descrimination of species than 

 the mere empirical rules at present practised, that we trust to be 

 excused for attempting to direct the attention of all those who have 

 it in their power to follow up the subject experimentally, to this 

 very desirable object. 



Although we must not hope to attain that degree of perfection in 

 systematic botany, which would probably be the immediate result 

 of our detecting the laws which regulate the limitation of species ; 

 yet much has been, and much more may unquestionably be achiev- 

 ed, through the means actually in our power, towards distributing 

 plants into natural groups, and pointing out the relations which such 

 groups bear to each other. Nothing has of late years contributed so 

 much to the progress of systematic botany, as the publication of se- 

 parate monographs of genera, tribes, end orders by different indivi- 

 duals. The number of species already known is so great, that no 

 single botanist can ever hope to examine in minute detail more than 

 a small fraction of them. He may, however,, become thoroughly ac- 

 quainted with the leading characteristics of every order, and of their 

 subordinate groups, and many of their genera, by merely examining 

 for himself a portion of the species which they each include. But 

 if, in addition to his general studies, he also directs his attention more 

 especially to some particular group, for the purpose of completely 





