162 MISSOURI BOTANICAL GARDEN. 



EXPLANATION OF PLATES. 



Plate 15. — Phoenix dactylifera. 1, Portion of an ovule at about 

 the time of pollination, showing the embryo-sac, tapetum and nucel- 

 lus, just prior to the disintegration of the last named. 2, Ovule 

 with the contiguous carpellary tissue to show the stylar canal leading 

 to the pollen-tube guiding tissue. The occurrence of tannin in specia- 

 quantity in this tissue in front of the micropyle is indicated by stip- 

 pling, as also in the embryo-sac, tapetum and inner integument, and 

 chalazal tissue. ' 2a, 2b, Transverse section through the ovule to 

 show the pollen tube canal, single above and double at the funicle. 

 2 c-e, Transverse sections to show the stylar canal at different 

 levels. The dots in the hypoderm represent tannin; stone cells cross- 

 hatched. Raphide cells are seen in 2 d. 3, Embryo-sac and tape- 

 tum at this time. The remains of the nucellus are seen as a cap over 

 the end of the embryo-sac. Digestion of the chalaza is proceeding 

 rapidly. 4, Pit formed of contiguous thick walls of adjacent cells; 

 the antipodal cells within this pit before degeneration of the basal 

 cell is apparent. 4a, The basal and middle cells degenerated. 5, 

 Ovule with one-celled embryo. Multinucleate parietal endosperm. 

 Its activity beyond the antipodal apparatus is evident. 6, Ovule 

 7-8 weeks after pollination. Distribution of tannin (the more densely 

 reacting tissues) shown by the dots; starch by cross-hatching. Deg- 

 let Noor. 7, Ovule, Deglet Noor, 8-9 weeks after pollination. 

 The post-chalazal growth of the endosperm is seen, together with the 

 general torsion of the ovule in the direction indicated by the arrow 

 points. Tannin indicated by the dots and conventionalized cells. 

 8. Endosperm cells at ten weeks, when the oil is first seen. 9, 

 The nuclei of the flattened endosperm cells of the superficial layer 

 bordering the utriculum. The manner in which the oil appears with 

 reference to the nucleus is evident. 



Plate 16. — Phoenix dactylifera. — 10, (Cf f. 8-9) Ovule, DegletNoor, 

 11.5 weeks. Endosperm growing inwardly to obliterate the utriculum. 

 Beginning of oil secretion. 11, Portion of transverse section of car- 

 pel and ovule to show the sutural sector in which a diffuse tanriin 

 reaction appears. 12, Longitudinal section of mature seed indicating 

 the topography. Ch. chalaza. End. endosperm. 13, Transverse sec- 

 tion through young seed through the chalaza. The chalazal tannin 

 tissue proper is indicated by dots. Tannin is present however, else- 

 where in the raphe and integuments. Same ovule as in f. 14. 14, 

 Young seed at the time when the closure of the endosperm is com- 

 plete. The distribution of oil about the embryo is indicated by the 

 size of the dots. 11 weeks after pollination. 14a, The region about 

 the embryo at about this time, in which no digestive action on the 

 cell walls is observable; a, Digestive zone; 6, Tension zone, where 

 cell divisions occur; 6', Thin-walled growing endosperm. 15, Ten 



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