Sexual Nuclei in Lilium Mart agon. 451 
throughout : one set fixed in one of the osmic acid mixtures, 
sometimes made up with a certain proportion of alcohol in 
order to ensure penetration, the other fixed in absolute 
alcohol. The first are stained by Flemming’s orange method ; 
the second with a mixture of methyl-green and acid fuchsin 
or with Renaut’s haematoxylic eosin preceded by orseillin. 
In a few cases other stains have been used for comparison, as 
Meyer’s haemalum. I have compared the two series at every 
stage and have formed my conclusions on the evidence of 
both. Further details of these methods are given in an 
appendix at the end. Moreover, I have been careful through- 
out to check the conclusions derived from a study of 
microtome sections by the examination of hand sections from 
absolute alcohol material. Deformations due to the em- 
bedding processes are absent from hand sections cut in pith. 
In one case only have I found it possible to examine 
living tissue with advantage. The contraction of chromatin 
to one side of the nuclear cavity during the process of 
formation of the spirem thread, which has been happily 
termed synapsis by Mr. J. E. S. Moore 1 , is treated by some 
histologists as a natural phenomenon, by others as artefact. 
As the contraction is invariably seen at the same stage in the 
development of both pollen mother-cell and embryo-sac 
nuclei, however prepared, I have for some time considered it 
as a condition existing during life, though doubtless subject 
to deformation during fixing and cutting processes. This 
summer however I obtained sections from fresh anthers on 
several occasions in which the chromatin of the pollen 
mother-cell nucleus could be clearly seen collected into a ball 
on one side of the nuclear cavity. The chromatin was 
identified by subsequent fixing and staining of the section. 
Division of the Vegetative Nucleus. 
The nuclei with which we are concerned in this paper are, 
as already stated, peculiar in exhibiting twelve chromatic 
1 J. E. S. Moore, Science Progress, vol. iii. p. 333. 
