Yendo . — On the Mucilage Glands of Undaria. 619 
arranged. It may be geometrically proved that the primary supraglandular 
space extends four times in area as each surrounding cell divides into two ; 
and that, when the cells on two opposite sides divide quicker than those 
in the other two, the results will be rectangular spaces. This is practically 
proved in the early stages of the formation of the spaces (Figs. 5, 6). 
As a frond grows further, the epidermal cells increase in number and 
size. As a fact, the cells surrounding a space multiply less quickly than 
those in a more remote position. The result is, as the geometrical principle 
may well prove, the radial arrangement of the cells with the space as the 
centre. Eventually the space gradually approaches to a round or elliptical 
area as it widens. Moreover, the cells bordering a space tend to elongate 
towards its centre as the mutual compression leaves that side entirely free. 
As a consequence, the cells surrounding a supraglandular space apparently 
converge towards its centre, as has been described by Okamura (Fig. 7). 
The contents of a primitive gland are a comparatively large nucleus 
and many colourless hyaline grains enclosed in a thin coating. As the 
gland grows larger the grains increase in number and remind one of 
a potato cell full of starch grains (Fig. 2). In some glands, during observa- 
tion under the microscope, the contents have suddenly turned into a homo- 
geneous mass, resembling, in a manner, the action of a strong potash 
solution upon the starch grains in a potato cell. The mass contained in the 
gland then made its way through the supraglandular space, changing into 
a mucilaginous matter, undoubtedly by the turgor-pressure of the gland. 
The semi-fluid which is ejected from the surface dissolves away by degrees 
in the surrounding medium. I was not able to detect any sort of opening 
in the external covering of the gland. But judging by the speed of the 
emission, the roofing membrane over the gland must have burst open 
to form a passage at that moment. 
At the moment when the glandular contents have been freed from the 
gland, the mass forms a globular body upon the supraglandular space and 
rests there for a considerable time. This is not recognizable, even under 
a high power of the microscope, before treating with the colouring matter, 
as the refracting power of the mass is nearly equal to that of water. 
Staining by aniline blue, however, shows the mass very clearly ; at the same 
time the mass remaining in the gland assumes the same colour. Hence in 
such cases, one globular body is seen on each side of an epidermal layer, 
constricted at the newly opened supraglandular passage. It is very 
interesting to note that the aniline blue can do nothing to the glandular 
contents before it has diffused into the homogeneous mass. In the microtome 
sections the glandular contents, in both young and old, are seen as a reticu- 
lated or areolar mass adhering to the inner surface of the wall, and there 
is hardly any difference in the degree of staining. 
Okamura suspected that the ‘ bag ’ might be a sort of excretory organ. 
