ROSACEA 353 



Pollination. — As a rule, the anthers and stigmas mature 

 simultaneously. There is abundant nectar secreted by a 

 fleshy ring on the margin of the receptacle, inside of the 

 stamens. Insects facilitate polhnation. Better yields are 

 secured, in the case of some dewberries, if they are planted 

 adjacent to another variety so that cross-fertiHzation will 

 result. 



Fruit. — The fruit (Fig. 147) of the genus is an aggregate. 

 The numerous pistils ripen into drupelets which cling to- 

 gether to a greater or less degree. In the dewberries and 

 blackberries, the drupelets are firmly attached to the recep- 

 tacle while in raspberries the drupelets readily separate from 

 the receptacle when the fruit is being picked, clinging together 

 in the form of a cup. The exposed surface and the angles 

 between the faces of each drupelet are pubescent in the rasp- 

 berry, and the faces themselves are glabrous. The sticking 

 together of the drupelets is due to the interlocking of these 

 crooked hairs. The blackberry and dewberry drupelets are 

 glabrous throughout. 



Geographical. — The Rubi are of wide geographic distribution; the greater 

 number of species, however, occurs in North Temperate regions. 



Classification. — The numerous members of the genus fall 

 into three groups which may be distinguished as follows : 



Key to Groups of Genus Rubus 



Drupelets firmly attached to receptacle, not separating from the latter when 

 fruit is being picked. 

 Stems upright; plant propagating by suckers; lower, outer flowers open 



first, Blackberries. 

 Stems trailing; plant propagating by tips; center flowers open first, Dew- 

 berries. 

 Drupelets readily separating from the receptacle when fruit is being picked, 

 clinging together in form of cup, Raspberries. 

 23 



