ROSACEA 361 



the receptacle. There are numerous stamens, as a rule, 

 sometimes a few or none; they are attached to the rim of the 

 receptacle, persistent in the fruit, and possess slender fila- 

 ments and small anthers. Pistils are numerous on the 

 smooth, convex, or conical receptacle which becomes modi- 

 fied m the fruit (Fig. 152, A). Each carpel bears a style 

 laterally placed (Fig. 152, B), and a single ovule. 



Fertilization, and Development of the Fruit.— Strawberries 

 are protogynous, that is, the pistils of a flower mature before 

 its stamens. Hence cross-fertilization is secured; and this 

 usually by insects. Non-fertilization or incomplete fertili- 

 zation is usually indicated by berries with hard, greenish, 

 undeveloped apices, so-called "nubbins." The true fruits 

 of a strawberry are the achenes (so-called "seeds") scattered 

 over the fleshy receptacle. Unless the ovules are fertilized, 

 the receptacle does not mature properly. This behavior is 

 the rule in most plants. When a sperm nucleus of the pollen 

 tube unites with the egg nucleus of the ovule, resulting in 

 fertilization, there is set into action a train of changes which 

 not only involve the ovule itself, but which extend to the 

 ovary wall, and, as in the strawberry, to the receptacle. 

 Undoubtedly, the stimuli are chemical in nature, but just 

 what they are and how they act is not known. 



The Mature Fruit. — The strawberry "fruit" (popularly 

 speaking) is an aggregate of true fruits. The fleshy part 

 of the "fruit" is receptacle, while the true fruits (botanically 

 speaking) are achenes partially imbedded in the surface of 

 the receptacle. In a lengthwise section (Fig. 152, A) of the 

 ripened fruit, the receptacle is seen to be composed of a 

 fleshy pith and cortex with fibro-vascular bundles between 

 them. It is in reahty stem structure. These bundles send 

 off side branches into the cortex, and some of them extend 

 to the achenes. The persistent calyx and epicalyx, and 



