

EMBRYO, SEED AND CARPEL IN THE DATE. 



107 



*Cji++ 



a week after pollination, active differentiation of tissues has 

 commenced at the apex of the carpel, which begins to pro- 

 ject beyond the bracts. The epidermis is thus more or less 

 exposed and is becoming strongly cuticularized. Hypodermal 

 tannin cells are evident here and there, and the layer of 

 stone cells is rapidly forming. Within the mesocarp, numer- 

 ous raphide bearing cells 

 have been formed, and the 

 tannin-idioplasts are more 

 strongly developed. 



Ovule. The ovule at the 

 time of pollination pre- 

 sents several matters of in- 

 terest from the present 

 point of view. Of the 

 nucellus nothing remains 

 but a cap of a single layer 



of cells, in a state of 

 rapid disintegration (f. 1). 



The bulk of the ovule is 

 of nucellar origin (f. 2, 5) , 

 and, after the disappear- 

 ance of the nucellus, may 

 be regarded as a chalazal 

 tissue. It thus comes about 

 that only the upper end 



a. Phoenix dactylifera. 



Longitudinal section through pistil 



of the embryo-sac is sur- at approximately the time of polli- 

 rounded by the integu- nation. The distribution of starch is 



ments, which form a shown by stippling -«, Tannin idio- 



. - plasts. s, Stone cells, r, Rhaphide 



crown resting on the top idioplasts . The stylar canal is seen. 



of it (f. 3). The micro- 



pyle is evident, and is lined by actively glandular cells, the 

 inner superficial cells of the inner integument. As seen by 

 the figure, the endostome juts forward into the exostome, 

 which is open. The anatomy of this region suggests the 

 explanation that the glandular tissue of the carpel facing 

 the exostome is a center of attraction for the pollen tube till 

 it reaches this point. The secretion, which is doubtless 



