718 Proceedings of the Royal Irish Academy. 



describes variations in number occurring in tbe nuclei of tbe game- 

 tophyte of Pellia epipliylla^ e.g. nine and seven instead of tbe normal 

 eiglit. 



It appears to be quite uncertain bow tbese differences in number 

 arise as all tbe nuclei of the plant must be derived ultimately from one 

 nucleus formed by tbe union of tbe male and female nuclei. Stras- 

 burger suggests (Ann. of Bot., Sept. 1894) tbat tbe variability in 

 number of tbe cbromosomes of tbe nuclei of tbe endosperm of tbe 

 Liliceae is due to tbe fusions wbicb. take place between tbe nuclei of the 

 endosperm. It may also be brought about by the formation of multi- 

 polar karyokinetic figures when two or more of the poles unite, and 

 the majority of the chromosomes pass to tbe polar area formed of the 

 union of two or more poles, leaving but very few for the single pole which 

 remains independent. This process I have observed in the endosperm 

 of Fritillaria imperialis. But neither of these methods of variation, 

 nor the variation which might follow from the direct nuclear fission 

 can be assumed as having probably caused the discrepancy in the 

 numbers observed either in. the embryonic or the sexual nuclei. 



In the hopes of being able to observe mitoses in tbe embryo and 

 the endosperm I pollinated a large number of the stigmas of flowers 

 of Lilium longiflorum with pollen from different or the same flowers. 

 In no case however was the embryo formed, although in several 

 sections the pollen-tubes were seen penetrating tbe micropyle, and one 

 preparation showed one male nucleus passing into tbe embryo-sac, while 

 the other apparently remained behind in the pollen-tube. In these cases, 

 immediately after fertilisation, the three antipodal- cells become placed 

 in such a position as to form a hollow cone round the large endospenn- 

 nucleus. The sac at the same time collapses latei'^Uy and elongates 

 downwards, and the endosperm nucleus travels deep into the nucellus, 

 and carries tbe three antipodal cells in front of it in the form of a cap. 

 The nucleus of these latter gradually becomes indistinct while tbe 

 whole protoplasm of the cells becomes more highly refractive, and 

 stains very deeply. A similar fate overtakes tbe other nuclei of the 

 embryo-sac, but usually somewhat later. 



"When no pollen-tube reaches the embryo-sac, a peculiar phenomenon 

 is sometimes observable. The central portion of the embryo-sac 

 becomes filled with a large number of nuclei formed by direct division 

 (fig. 18). From my sections it is impossible to say with certainty 

 whether these arise from division of the lower polar nucleus, or from 

 the endosperm nucleus, formed from the fusion of the upper and lower 

 polar nuclei, but from the preparations the former seems the most 



