274 Cook : Embryo-sac of Passiflora adenophylla 



filling it (figs. 6, 7, and 8) and becoming very much twisted and 

 tangled in the process. The growth of the tube seems to be so 

 vigorous that its entrance into the embryo-sac usually results in the 

 complete absorption of the egg-apparatus (figs. 6 and 7) and 

 eventually of the entire contents of the sac. In those cases in 

 which the tube does not burst, the egg-apparatus begins to dis- 

 integrate immediately upon the entrance of the tube (figs. 6 and 

 7). The sac then enlarges and the tube makes a vigorous growth, 

 enlarging in both diameter and length and eventually filling the 



sac with a very much tangled mass (fig. 8), which apparently draws 

 its nourishment from the nucellus. It stains very deeply with 

 haematoxylin. In the material from which this study was made, 

 this condition was the rule and not the exception. It appears 

 that the parasitic nature of the pollen-tube in these cases has de- 

 veloped in excess of the usual manner and that instead of per- 

 forming the function usually performed by this organ^ it really 

 prevents the formation of the embryo. 



In some instances the pollen-tube acted in the usual manner 

 (figs. 3 and 4) and several cases were observed in which the egg 

 had the appearance of having been fertilized (fig, 4), A satis- 

 factory study of the embryo was impossible because of the lack of 

 material. 



A number of sacs were observed in which a non-cellular endo- 

 sperm had been formed (fig. 9). In no case was the endosperm 

 and an abnormal pollen*tube observed in the same sac. 



Delaware Agricultural Experiment Station, 

 Newark, Delaware. 



Hxplatiation of plate 19 



Fig. I. Four-nucleate embryo-sac. 



Fig. 2. Eight-nucleate embryo-sac. 



Fig. 3. Micropylar end of the sac, showing the egg, the pollen-tube and two 

 sperm-nuclei. 



Fig. 4. Micropylar end of the sac, showing the fertilized egg, the two polar nuclei 

 in the act of uniting, and one sperm-nucleus. 



Fig. 5' Union of the two polar nuclei and one sperm-nucleus. 



Fig. 6. Micropylar end of the embryo-sac, showing the entrance of the pollen- 

 j_ube without rupturing, and the egg-apparatus in early stage of disintegration. 



Fig. 7. Micropylar end of the erabryo-sac, showing later stage in the growth of 

 the tube and the further disintegration of the egg-apparatus. 



Fig. 8. Later stage in the development of the embryo-sac, showing it almost 

 entirely filled by the excessive growth of the pollen-tube. 



Fig. 9. The endosperm. 



