276 BOTANICAL GAZETTE [October 



at least four days after pollination, and fertilization is possible within 



EMBRYOGENY 



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The fusion nucleus gives rise to eight free nuclei^ more or less 

 unequal in size, and three to five of the largest ones surround them- 

 selves by a wall and produce embryos. The free nuclei are either 

 arranged in a row down the middle of the egg, or more frequently are 

 scattered through it. The lower ones in general successfully produce 

 embr}'os, although a few instances were noted in which the lower ones 

 did not function further than the one-celled stage, the micropylar ones 



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ten hours after pollination, it has been very difficult to secure fertili- 

 zation and early proembryonal stages. Only those ovules which 

 have been incompletely pollinated by having the pollen lodged for 

 a time in the long tubular micropyle, and later dislodged and reaching 

 the pollen chamber, can by any possibility show fertilization. From 

 the nature of things such a delay in pollination must be very rare, 

 although the ovules are peculiarly fitted to have such delays occur. 

 Among over 2800 ovules sectioned at the time when fertilization was \ 



expected, only two {fgs. 4 and 5) showed early stages. 



The pollen tube forces its way between the neck cells of the arche- 

 gonium, rarely destroying them in its passage. Only in one or two 

 instances were the low^r neck cells destroyed. In ]ig. 4 the lower and 

 apparently double nucleus shows the all but complete fusion of the 

 sperm and the egg nuclei. The small nucleus lying immediately 

 above the fusing nuclei is the ventral nucleus; the one immediately 

 above it is the second male nucleus, which in this instance has passed 

 deeper into the egg cytoplasm than usual. Fig. 5 shows the fusion 

 nucleus with fragments of the ventral nucleus lying above it. The 

 second male nucleus, with the stalk nucleus and tube nucleus lying 

 immediately below it, is seen in the upper end of the egg. The stalk 

 nucleus and the tube nucleus soon disappear. The second male 

 nucleus does not ordinarily penetrate deeper into the egg than is 

 shown in fig. 5, but undergoes its final changes here- The dense 

 mass of cytoplasm surrounding the fusion nucleus and extending 

 downward through the egg is well shown in figs, 4 and 5. This mass 

 first appears as a densely staining spherical body in the upper third 

 of the central cell, and disappears with the formation of proembryos. . 



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