ON THE DUMETOUUM GROUP OF RUBI IN BRITAIN. 151 



the protean R. fusco-ater (Weihe, as the plant is interpreted by Pro- 

 fessor Babington) should not follow diversifolius into the dumetose 

 group. This may be a consideration for the future ; as I am convinced 

 we are still far from finality, and that our group will hereafter receive, 

 even in this country, many new varietal additions. Some of these 

 are now probably before me in Mr. Baker's excellent series, but it is 

 always dangerous in rubiology to describe merely from dried specimens. 

 The golden rule of our Bramble-collecting guild ought to be, see your 

 individual plant always in its groioing state. 



The dumetornm group are Brambles of the hedge, and essentially, 

 to adopt Mr. Watson's term, septal. They are not of the wood, or of 

 the open ground ; contrast, for example, R. Borreri for a heatli, or R. 

 Guntheri for a wood, form. A. good compendious definition of the 

 group as a whole is, that it represents corylifoUus in the glandulose 

 series. 



As contrasted and distinguished from the other Glandulosi, through 

 all its series of variations, dmnelorum may be chiefly recognized — 1. 

 By its weak, and consequently trailing, long, nearly round, bai-ren stems, 

 with a decided tendency to be bloomy.* 2. By the irregularly deltoid 

 dentition of the leaflets as in corylifoUus ; the terminal one being 

 round or broad-obovate with a point, the lower four so shortly stalked 

 that they usually overlap a great deal. 3. By the petals 3-4 lines 

 broad. By the flowering beginning at the same time as corylifoUus, 

 ccesius, and suberectus, and being continued in a very irregular way, 

 lasting till very late in the year. 4. By the black fruit and carpels 

 more irregularly fertilized, like those of coryUfoUus, and by the drupels 

 fewer and larger than in any other species except casius and coryli- 

 foUus. 



Within this range the principal variation is in — 1. Stem armature 

 (enormous variation here in ([uantity of prickles aciculi and seta?, and 

 whether or no hairs are present on the barren stem and panicle rachis). 

 2. In the size of leaf and clothing of its underside. 3. In shape of 

 panicle. 4. In sepals, whether erect or adpressed. 



Our new provisional arrangement of dumetoruin may be then thus 

 stated : — 



a. concinnus, Baker = luherculutns, Bab. ex parte. The Thirsk 



* Note here that these two points define the position of this group. The 

 round stem shows a corylifolian, the bloom a ccesian, alliance. 



