212 Rivett.— The Cytoplasm in the Cells of A licularia sc alar is. 
of longitudinal sections through the growing point, cut in wax, from material 
fixed with osmic acid for twenty-four hours, and taken up through alcohol 
and xylol, are examined on the slide, mounted up in Canada balsam without 
further staining, then the only cytoplasmic bodies which show up clearly are 
the refractive granules. They show up as minute black spheres, which are 
more numerous in the cells of the growing point than in those of the older 
leaves, though they are still present in the latter. They are arranged in the 
peripheral layer of the cytoplasm and are also associated with the empty 
sacs which mark the limits of the oil-bodies. Thus they must be of different 
material both from the ethereal and fatty oils which disappear in the 
processes of dehydrating and embedding, even though partially fixed with 
osmic acid. There is no indication in such an 
unstained slide of the vacuolar structure of 
the protoplasm which would indicate the for¬ 
mation of the oil-bodies. 
After bleaching with hydrogen peroxide 
and staining with the triple stain (safranin, 
gentian violet, and orange G) certain other 
points emerge. The refractive granules stain 
brightly with safranin (thus resembling the 
nucleolus), but they are now much more con¬ 
spicuous in the older cells than in those nearer 
the growing point (see Text-fig. 3). They 
are associated with the empty oil-sacs of the 
mature cells and are also arranged around the 
^ __ „ cell-walls. In the growing point they are 
Text-fig. 3. Mature cells n & r J 
in longitudinal section from base very much smaller and are frequently masked 
granule^stained^ith safnmfn. ^ = b V the 0ran g e colour ’ which stains the S el 
material of the cytoplasm. The cells of the 
growing point are filled with stained contents, which are mainly aggregated 
in the nucleus, whilst around it is a more or less homogeneous or exceedingly 
fine granular mass. There is no indication of a spongy network or of 
a vacuolar structure; the material of the cytoplasm consists of masses of 
grains so exceeding fine as almost to make up a homogeneous substance. 
This may be because both the grains and the gel in which they are em¬ 
bedded stain in the same way (see PL VI, Fig. 5 a, 1, 2, and 3). 
The upper cells of the first two leaves show more differentiated 
contents ; the nucleus still appears large in comparison with the total bulk of 
the cell and usually occupies a central position. There is a slight indication 
of vacuolar structure around the nucleus, but in the cells of the third and 
fourth leaves this is more evident (PI. VI, Fig. 5 b, 4). In between the 
central nucleus and the peripheral layer of chlorophyll granules there is a 
vacuolar structure resembling the familiar f spongy network ’ of the proto- 
