150 



ELEMENTS OF STRUCTURAL BOTANY. 



with it, and forming what is then called the raphe. Fig. 

 211 represents this condition, r being the raphe, s the 

 chalaza, and the other letters corresponding to those in 

 Fig. 210. 



Sometimes the curving of the ovule upon itself is not 

 carried to this extreme, and an intermediate form is 

 presented, as in Fig. 212. 



ai 



Fiff. 212. 



Fig. 210. Fig. 211. 



If the ovule remains straight it is said to be orthotro- 

 pous ; if completely inverted, anatropous ; if half bent 

 over, campylotropous. 



247. Pollination. The process of fertilization, by 

 which the ovule is converted into the seed, has been 

 briefly described in Chapter II. A few words may be 

 added here upon pollination the process of supplying 

 pollen to the stigma. In very many flowers which have 

 both stamens and pistil (and hence called hermaphrodite), 

 the process is very simple. Either the anthers and 

 stigma are so close together that the pollen cannot fail to 

 be deposited upon the stigma immediately upon the 

 opening of the anther, or the stigma is upon a lower level, 

 so that the pollen drops upon it, or, in special cases, as in 



Figs. 210, 211, 212. Diagrams of orthotropous, anatropous, and campylo- 

 tropous ovules. (Prantl.) 



