﻿212 



BOTANICAL GAZETTE 



[march 



nucellus nearly to the extremity of the fibrovascular bundle {figs. 4,5). 



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\ 



The 



migration 



of the nuclei into the tube and its relation to the 



fibrovascular system suggest that it may have a nutritive function, 

 serving as an haustorium. This suggestion is further supported by 

 the presence of fine granular material in the tube and in the cells 



adjacent to the fibrovascular bundles 

 and the tube. If these are the granules 

 of an organic acid, as their staining 



of 



Fig, 4. — An embryo-sac in 

 which the haustorial tube is fully 

 formed and the divisions of the 



qualities indicate, or some form 

 plastic food material, then the migra- 

 tion of the nuclei may be considered a 

 chemotactic response analogous to the 

 growth of the pollen tube and the 

 entrance of the antherozoids into the 

 embryo-sac. Vesque (2, p. 304) found 

 haustorial appendages in the embryo- 

 sacs of Scrophulariaceae, Santalaceae, 

 and Lathraea, and comments upon the 

 parasitic nature of the embryo-sac in 

 certain instances. A recent writer (13) 

 reports the presence of haustorial ap- 

 pendages in certain of the Araliaceae. 

 After the divisions of the macro- 

 spore are completed, the egg-cell and 

 synergids move up to the apical end of 

 the embryo-sac; the definitive nucleus 

 also moves out, but often only to the 

 mouth of the haustorial tube, some- 

 times to the middle of the embryo- 

 sac; the antipodal nuclei usually remain 



macrospore are completed: /. fibro- * ^i_ . r 



1 u ji , , . , m the tube. 



vascular bundle; h, haustorial tube. 



X 360. Coincident with the divisions of 



the macrospore and formation of the 

 embryo-sac haustorium, there is a rapid increase in the amount of 

 nucellar tissue, an enlargement of the embryo-sac cavity, and a prepa- 

 ration for fertilization. 



The columnar cells which serve as 



centae and to the macrosporangium are very 



an epidermis to the pla- 



large 



on that part 



which covers the ridges of the placentae and the basal part of 

 the stalk of the macrosporangium. From these cells there exudes 



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