Wolfe . — Cytological Studies on Nemalion . 609 
Methods. 
The chrom-acetic mixtures gave entire satisfaction as killing fluids. 
Material fixed when collected was suitable for most purposes, but a greater 
abundance of dividing nuclei was seen in that kept in running water in the 
laboratory and killed at various times during the night. Material killed in 
2 °/ D formaldehyde in sea-water and gradually transferred to pure glycerine 
kept its colour perfectly, and, except for a slight shrinkage and the loss of 
the small amount of chlorophyll, presented much the appearance of the 
living plant. 
In connexion with the study of fertilization a method was employed 
which made it possible to examine a great number of procarps at all stages 
of development with a much smaller expenditure of time and labour than 
would have been the case if sections had been used. Young tips were 
crushed in water under a cover-glass and on a slide that had previously 
been treated with fixative ; the cover was then removed and the water 
on the slide allowed to evaporate. The gelatinous nature of the wall 
prevents the contents of the cell from being affected by this treatment even 
when the albumen has hardened sufficiently to hold the filaments firmly in 
place. Preparations made in this way were then double stained in safranin 
and gentian-violet by the usual method and mounted in balsam. This 
was usually accomplished without any shrinkage whatever; and, as the 
decolorization could be controlled with the aid of the microscope, a finer 
differentiation was secured than is possible by staining in bulk. 
For the study of nuclear detail iron-alum-haematoxylin after the 
method of Heidenhain gave excellent definition, and, in addition, was easy 
to control. Erythrosin, or eosin, was used where a plasma stain was 
desired. Flemming’s triple stain was repeatedly and persistently tried, but 
in no case were results secured in any way approaching those obtained with 
the Heidenhain. 
Sections 3 /x in thickness were used in most cases, but in order to 
establish certain points it was occasionally found to be necessary to cut 
them as thin as 1 /x. 
The Cell. 
The cell-wall is relatively thick, and under high powers is evidently 
lamellate in structure. It has been figured by Wille (’ 94 ) as a double wall, and 
certainly such an appearance may be seen in certain cases (PL XL, Fig. 24). 
It is by no means easy, however, to determine whether this appearance 
is due to the actual presence of a double wall, or whether it may not more 
probably be a misleading appearance resulting from its often very distinctly 
lamellate structure. The usual tests produce a characteristic though 
delicate cellulose reaction, the weakness of which is evidently due to 
the partially gelatified condition of the walls. 
