in the Root- Apex of Phctseohts . 43 
the centre,.’ and that ‘there may be one, two, three, or many cavities of 
various sizes and arrangement V 
Macfarlane 2 regarded the vacuoles as endonucleoli and ascribed to 
them an important part in the nuclear economy, and he still insists on their 
probable importance in living cells, and suggests that they play a ‘ special 
part in furnishing to the nucleolar substance some ferment or compound 
which may be utilized during the division period 3 .’ 
Mann 4 regards the endonucleolus as ‘the trophic centre for all the 
organs concerned in assimilation and dissimilation,’ and says that it plays 
an important part in the conjugation of cells. 
Cavara 5 contends that the vacuoles indicate the separation of the 
nucleolar substance into two distinct parts, chromatin and plastin, and 
Zacharias, who is opposed to the chromatin-plastin theory of the nucleolus, 
nevertheless concludes that it appears to consist of two distinct substances, 
a more refringent vesicular substance surrounded by a homogeneous, less 
refractive substance 6 . 
Chamberlain has described a case in which the central, less deeply 
stained portion appeared to be separable from the outer, more deeply 
stained peripheral part, for ‘ there seemed to be a crack in the nucleolus, and 
upon applying a gentle pressure the central portion came out of the shell 7 .’ 
In haematoxylin-stained specimens of Phaseolus it is very clearly seen 
that the outer layer becomes more deeply stained than the vacuolar sub- 
stance ; in some cases there is a very marked distinction between them, 
and in some nucleoli the vacuolar substance is in contact with the exterior 
through an opening in the outer layer on one side of the nucleolus (Fig. 5). 
In methyl green and fuchsin the nucleolus stains bluish-red, the nuclear 
network red, and in specimens from which the stain has been well washed 
out the outer layer of the nucleolus is coloured light blue, the vacuolar 
portion remaining colourless or nearly so. Similar results are obtained 
with methyl green and eosin. In gentian violet the outer layer is deeply 
stained violet and the vacuolar portion light blue. But in many of the 
larger nucleoli the gentian violet shows up a more complex structure. 
In such cases we find a deeply stained thin outer layer surrounding a less 
deeply stained inner layer, and in the centre one or more deeply stained 
masses which are irregular in shape, with coarse radiations into the lighter 
stained part, or even exhibit a structure akin to a coarse network, which 
recalls the description given by Carnoy of his nucle ole s-noyaux. 
The existence of a chromatin-like substance in the nucleolus is 
indicated by the fact that in all these stains the chromosomes stain like the 
nucleolus, except that there may be a difference in the intensity of the 
1 Memoir on the Nuclei, Formation, and Growth of Vegetable Cells, translated from Schleiden 
und Nageli’s Zeit* f. wiss. Bot., 1844, by W. Henfrey, p. 239. Ray Society, 1845. 
2 Loc. cit, 1882-5. 3 Loc. cit., 1901, p. 194. 4 Loc. cit., 1892, p. 396. 
5 Loc. cit. 6 Loc. cit., 1885. 7 Loc. cit., Bot. Gaz., 1899. 
