35° UOTANY OF CROP PLANTS 



belief that stamens are leaves, morphologically. The pro- 

 duction of supernumerary petals is known as "doubling." 

 The stamens are numerous, distinct, and attached to the 

 margin of the toral disk (Fig. 147). The anthers are small 

 and two-celled. The carpels are usually numerous and dis- 

 tinct, or rarely attached to the calyx. The ovary is one-celled 

 (rarely imperfectly two-celled) with a terminal or lateral style, 

 and with from one to many ovules. 



Fruit. — The fruit is a follicle in Spircea, an aggregate of 

 drupelets in raspberry, blackberry and dewberry, or an 

 aggregate of achenes in strawberry and rose. The follicle 

 is a pod-like fruit, with one carpel, which opens along one 

 side only and usually bears numerous seeds. The true pod, 

 characteristic of the pea family, is a one-carpelled fruit, 

 which spHts along two sides. It will be remembered that 

 the capsule has several carpels. A drupelet is a small 

 drupe — a one-seeded fruit with a fleshy mesocarp and stony 

 endocarp. 



Key to Important Genera of Rosacea 



Fruit not inclosed in a hollow receptacle, i.e., the calyx not constricted over 

 the fruit. 

 Carpels becoming follicles, Spima. 

 Oorpels become small drupelets crowded on a fleshy' receptacle, Rubus 



(raspberry, blackberry, dewberry). 

 Carpels becoming dry achenes. 

 Style becoming long and plumose, Cercocarpus (mountain mahogany). 

 Style short. 

 Receptacle fleshy in fruit, Fragaria (strawberry). 

 Receptacle not fleshy in fruit, Potentilla (five-linger or cinque-foil). 

 Fruit inclosed in a hollow receptacle, i.e., the calyx constricted over the 

 fruit, Rosa (rose). 



RUBUS (Raspberry, Blackberry, Dewberry) 



Stems. — The plants of this genus are usually shrubs, 

 rarely herbs (Rubus Chamcemorus, cloudberry, knotberry or 



