175 



to do otherwise than honour Dr. Bell Salter's powers of discrimma- 

 tion; but I must say this, that no "three days'" nor even three years' 

 observation of dried Rubi in herbaria, are sufficient to enable any per- 

 son to speak with absolute confidence in doubtful or difficult cases, as 

 to the specific distinctions of the fruticose brambles, who has not like- 

 wise for many years narrowly watched them in a growing state. This 

 is a hard saying for railroad botanists, I confess, but in my own case, 

 I will candidly say, prohatum est. I have myself carefully regarded 

 the subject for ten years, and am on some points doubtful even now. 

 Dr. B. Salter has very handsomely expressed his general agreement 

 from his own experience with my exhibition of the mode of growth of 

 the British fruticose Rubi, contained in my paper in the ' Transactions 

 of the Edinburgh Botanical Society,' but " takes the most decided 

 exception" to the modification which habit exercises upon apparent 

 specific character. The Doctor has however altogether omitted to 

 say what characters he considers unchangeable^ and what are varia- 

 ble. Now this is a point of the utmost importance in the enquiry, 

 and on this everything hinges. I fear it would take up too much 

 space to go fully into the subject on the present occasion, but this, at 

 least, my experience fully warrants me in affirming, that the glandu- 

 losity of the panicle is not to be depended upon as an unalterable 

 specific character in the Rubi. Hence, strange as it may appear to 

 Dr. B. Salter, R. radula may present itself without a gland^ and R. 

 suberectus exhibit abundance of them, contrary as this is to their cha- 

 racter generally. Indeed, I can state confidently, that I have traced 

 R. caesius on the one hand from being moderately glandular, to a state 

 profusely so, and on the other, to a variety where not a gland can be 

 seen, even with a lens. So in the form I have called R. sublustris,* 

 (equivalent to Smith's R. corylifolius, and Leighton's " second form 

 of R. rhamnifolius"), where in a full sunny exposure abundant glands 

 are induced on the panicle, peduncles and calyces, while in the shade 

 the pubescence smothers and entirely obliterates the glands. Even 

 the barren stem is thus affected, the exclusion of light often prevent- 

 ing the appearance of setae and glands, which a bright sun and power- 

 ful temperature would call forth. This fact should hint caution to the 

 namers of dried specimens, and indeed collectors should be precise 

 in stating whether their specimens were gathered in a sunny expo- 

 sure or in the shade. 



* This is substantially the same form as that I called R. caenosus in the Edin- 

 burgh Transactions, the name seeming more appropriate. 



