342 TKANSACTIONS AND PROCEEDINGS OF THE [Sess. lxiv. 



structures stand to one another is to be found in a paper 

 by the same author (5) published in 1891, and containing 

 an account in considerable detail of the anatomical features 

 of the fully formed root rudiment, without, however, 

 touching on the question of its origin or mode of develop- 

 ment, while he barely does more than refer to the lenticel, 

 which he regards as raised on a small papilla, the pro- 

 jection of which above the general surface of the stem is 

 accounted for by the growtli of the underlying rootlet. 



The root itself he correctly describes as exhibiting all 

 the anatomical characters of a typical root of the species, 

 though it remains in a state of arrested development so 

 long as the environment of the stem is normal, and only 

 commences to elongate under the influence of excessive 

 moisture. 



A superficial examination of any portion of the mature 

 stem of S. Dulcamara will in most cases show the surface 

 to be covered with the small papilla' above mentioned, 

 which on the older and thicker portions often reach a 

 height of 1 or 2 mm., and appear as rounded warty 

 excrescences,. with rough, nearly vertical, sides, and flat or 

 slightly pointed apices. 



Each papilla is accompanied by one or more small dark- 

 coloured lenticels, placed either close to its base on the 

 surface of the stem, in the angle which it makes with the 

 stem, or even on the sides of the papilla itself, though but 

 r'arely on its apex, from which, however, the oiiter layers 

 of cork are not unfrequently abraded, giving a rough 

 surface, at first sight not unlike a lenticel, but easily 

 distinguishable therefrom by the entire absence of the 

 characteristic complementary cells ; and this arrangement 

 of parts, which may be looked upon as typical of the 

 mature papilla, is generally to be found on all stems 

 of more tluin two years of age. 



On stems in their second year of growth the papilhe are 

 in general less sharply limited, and appear as rather low 

 dome-shaped protuljerances with a smooth rounded surface, 

 Ijearing on tlieir Hanks a pair of small lenticels. These are 

 somewhat elongated in the direction of the axis, and are 

 usually placed near the base of the protuberance, though 

 their number and relative positions may vary considerably, 



