620 Yendo . — On the Mucilage Glands of Undaria . 
It is not very clear to me how he came to think of finding an excretory 
organ in an alga. It is now established that the mass contained in the 
‘ hyaline bag ’ is not a coloured solid substance while in the living state, but 
a colourless, plastic semi-fluid. The chemical properties, however, of this 
mass are not yet satisfactorily known to me. But I have ample reason 
to believe that the problematic cell is a gland secreting a mucilaginous 
substance. 
It is rather doubtful to me whether the mucilaginous substance actually 
flows out in nature through the supraglandular space in the manner just 
alluded to above. What I have observed might have been due to an 
unusual turgescent state of the glandular cells during the preparation. 
The thick membrane roofing over the gland seems to be strong enough 
to hinder the free emission of the substance. But judging from the fact 
that the compressed matter in the gland seeks its way through the thick 
membrane and not by bursting the thin coating, it is more legitimate 
to believe that the weakest part of the membrane is at the roof, and that 
the contents pass out slowly by osmotic action through this part. 
The fronds of Undaria , Hirome , and Undariopsis have been described 
as lacking the mucilage canals. Yet the plants belonging to these genera 
are highly gelatinous to the touch while in the fresh state. That it is due 
to the mucilage thinly coating the surface of the frond may be proved by 
the reaction of an aniline blue solution. A fresh frond is dipped in toto in 
the solution : the mucilage is stained, and at the same time coagulates into 
a flaky matter. This coagulated matter may be easily brushed away, 
leaving the surface of the frond highly resistant to friction. 
So far as researches on the mucilage ducts of the other Laminariaceous 
plants extend, there is no positive proof that the ducts have free openings 
in the surface of the frond. The canals may terminate at the epidermal 
layer, but are always closed at the end by a single layer of cells. We are 
led to believe that the mucilage is squeezed out through this layer. This 
suggests the probability of the above hypothesis relating to the gland under 
consideration. 
It was remarked above that the glandular contents stain very well 
in the fresh material after the granular structure has disappeared. This 
may lead us to suppose that the contents had changed their chemical 
properties before and after the transformation. It must be borne in mind, 
however, that aniline blue stains plasmolyzed cell-contents much deeper 
than those in a turgescent condition. This is true for all living cells of 
Algae, so far as my experience extends. The exceptions are met with in 
special absorption-organs such as the hairs of the Phaeophyceae. So also 
in many phanerogamic cells. The glands whose contents have changed 
into a hyaline homogeneous mass might lose some of their contents through 
the supraglandular coating. The plasmic membrane coating the inner 
