616 Yendo . — On the Mucilage Glands of Undaria. 
tissue consists of separate hyphal cells, often ending in a cortical cell. 
They are very loosely arranged, and the space between them is filled up 
with a gelatinous matrix. 
The chromatophores are also found in the cortical cells. Large 
numbers of the hyphal cells lack the chromoplasts ; but one or two of the 
grains may often be found in the form of a ring, closely fitted to the inner 
surface of the cell- wall (PI. XLVIII, Fig. 2). Here and there in the 
epidermal layer an embryonal stage of the hairs may be met with in a 
depressed circular area. In the well-grown sporophyllous fronds numerous 
hyaline corpuscles are found in the cortical cells. These corpuscles turn 
yellowish brown in the dried or formalin specimens. 
To understand the relative position of a gland and the space above it, 
or supraglandular space as it may be called, it was found best to apply a 
special staining matter to the former. The glandular contents stain much 
deeper than the surrounding tissue in aniline blue or in haematoxylin. A 
part of a frond is dipped in either of the colouring materials for a few 
minutes. It is then washed thoroughly in a diluted acid alcohol. In the 
case of anilin blue almost all parts of the tissues except the glandular 
contents are decolorized ; in haematoxylin, the glandular contents are 
stained a purplish colour and the nuclei of other cells a bluish violet, while 
the cell-walls remain almost unstained. When a piece thus treated is 
observed from the surface under a moderate power, the position of the 
space above a gland is satisfactorily recognized (Fig. 1). 
In the earlier stages, each supraglandular space is situated just above 
the centre of the gland. But as the latter grows larger, the space also 
increases in size, elongating, at the same time, into an elliptical or linear- 
oblong area. The longer axis is always parallel to the margin of the 
pinnule. In the elongated old glands, the supraglandular spaces are in 
many cases stretched in the direction following the glands and are situated 
above their middle or terminal point. It has been ascertained that the 
most elongated glands lie near the margins of the pinnules, in such a degree 
as often to join with an adjacent one. There is little doubt that the 
direction of the elongation of both the supraglandular spaces and the 
glands is a consequence of the growth of the pinnule. 
As soon as a ligule has appeared at the transitional region, the forma- 
tion of glands begins to take place in it. Numerous completed glands are 
already to be found mingled with younger ones, when a ligule has attained 
to the length of 1 cm. The table given above reveals at once that the 
glands are formed in large numbers in the pinnules of a young plant and 
that they become rarer in the adult pinnules, as the pinnules increase in 
area, with few additional glands. The present writer obtained the best 
results by the following method of treatment, among various others, in 
searching after the mode of development of the glands. 
