FERTILIZATION 



187 



the micropyle and fits like a hood or canopy over the nucellus, 

 serving as a sort of bridge for the pollen tube (Fig. 109). Often 

 the cells of the obturator may be greatly elongated or may have 

 a glandular appearance (Fig. HOC, D). 



Some other structures having a different origin but serving the 

 same function may also be included under the general term ob- 

 turator. In the Thymelaeaceae (Fuchs, 1938) the cells belonging 

 to the base of the stylar canal elongate and grow down as hairy 



Fig. 111. Development of obturator in some members of Thymelaeaceae. A, 

 Daphne laureola, l.s. pistil. B, same, part of ovary with cells of obturator pro- 

 truding downward into micropyle. C, more advanced stage, showing path of 

 pollen tube. D, Passerina pectinata, l.s. part of ovary, showing obturator (mi = 

 micropyle). (After Fuchs, 19SS.) 



processes approaching the nucellus (Fig. 111). In Pilea (Fagerlind, 

 1944) a tuft of papillate cells extends from the base of the style to 

 the apex of the ovule, coming in intimate contact with the latter. 

 In Myriocarpa and Leucosyke (Fagerlind, 1944), on the other hand, 

 it is the cells of the inner integument which elongate upward and 

 penetrate into the stylar canal (Fig. 110A, B), forming what may 

 be called an integumentary obturator. 



Usually there are no special modifications in the cells lining the 

 micropylar canal, but sometimes, as in Berkheya (Gelin, 1936), 



