38 Mr. C. C. Babington on the British Rubi. 



that it is really a distinct form constituting what, in this genus, 

 we consider as a species. The characters of the living plant are 

 so conspicuous as to distinguish it at a glance from the other 

 brambles amongst which it grows. It will probably soon be 

 found in other places. 



11. R. leucostachys /3. vestitus. 



R. villicaulis a. et d, Bab. Man. ed. 1. 95. 



R. Leightonianus, Bab. Ann. Nat. Hist. xvii. 240, Man. ed. 2. 101. 



The following observations quoted from a letter (dated Oct. 26, 

 1847) addressed to me by my friend Mr. Leighton, appear to prove 

 indisputably that my R. Leightonianus is only an extreme state 

 of R. leucostachys. He deserves credit for the pains which he 

 has taken to elucidate this subject, but I must deplore that his 

 acuteness has been so successful in this particular case, for he 

 has thereby frustrated a proposed commemoration of himself and 

 his labours. This is a remarkable instance of the advantage of 

 carefully distinguishing and describing forms, as thereby attention 

 is drawn to them and a better knowledge of the limits of species 

 attained. If typical specimens of R. leucostachys and R. Leigh- 

 tonianus were alone seen, probably no botanist would doubt their 

 distinctness; but when we trace R. leucostachys changing, in 

 shady places, into R. vestitus, and that in denser shade acquiring 

 the very thin large remarkably dentate and pale leaf of R. Leigh- 

 tonianus, we become convinced that only one variable species is 

 before us. This conclusion is additionally enforced by the con- 

 current variation in the prickles. In the autumn of 1847 I was 

 led to suspect that R. Leightonianus would be proved to be only 

 an extreme state of R. leucostachys, from a difficulty which occur- 

 red to me when endeavouring to distinguish it from R. vestitus 

 in a dense wood in Herefordshire. Shortly afterwards I received 

 Mr. Leighton's remarks, accompanied by a series of specimens, 

 and my suspicions were converted into certainty. 



Mr. Leighton remarks as follows : — " If you examine the bar- 

 ren stem of R. leucostachys ft. vestitus, growing in rather exposed 

 situations, you will find the prickles on the middle and upper 

 portions large, equal, fully developed, and confined to the angles 

 or nearly so ; but on the base of the stem the prickles are much 

 more numerous, smaller, and scattered on all sides. The leaves 

 have dense white tomentum on their under surface; and the 

 prickles on the petioles are hooked and strong. 



" On young plants, or those growing in shady woods, espe- 

 cially if moist, the barren stem presents throughout much the 

 appearance of the base of the same part in exposed plants in its 

 greener colour, and the inequality, slenderness and scattered po- 

 sition of the prickles. The leaves also are thinner and green on 



