412 Collins.—The Structure of the Integumentary System of the 
micropyle fail to resist the passage of solutes. In the ovule these walls 
bounding the micropyle were found to be cuticularized. 
As an aid to absorption at the micropyle, the lodicules with their 
marginal fringe of long hairs serve in the early stages to draw up and hold 
liquids over the micropylar area. 
To turn now to consider the other possible point of entry, the tract of 
chalazal tissue in the furrow where it meets the dorsal margin of the 
scutellum. At this point the chalazal tissue, reduced to a group of cells, 
comes practically flush with the surface of the grain, and once traversed, 
gives entry to both embryo and endosperm. It has been shown that these 
chalazal cells form a glandular group. In the mid region of the grain, in 
addition to this group, there is a mass of closely compressed cell-walls 
directed towards the centre of the grain. This mass represents the crushed 
remains of chalazal cells engaged in distributing supplies to the endosperm 
of the ripening grain. (See Figs. 2, 3, 4, and 6.) As previously mentioned, 
the nucellar epidermis is absent from the chalazal tract. The mass of cell- 
walls would presumably hinder the passage of liquid after it had passed 
the glandular group of cells. That it would further differentiate between 
solute and solvent is possible, but it is doubtful whether it would prevent 
all passage of the solute. It seemed clear that solutes were able to pass 
the glandular cells, for a precipitate of silver chloride was seen at the base 
of the sheaf-like mass of cell-walls after successive immersion in silver 
nitrate and sodium chloride for periods of 48 hours. Generally, however, 
after prolonged steeping in these solutions, there was good evidence of the 
further penetration of the solutions into the mass of cell-walls, and the 
arrangement of tissue along the course of the furrow would allow of a much 
quicker entry at the germinal end. Occasionally a precipitate was seen 
between the tegmen cuticles on the flanks of the furrow, and it was surmised 
that the compressed mass of cell-walls offered very considerable resistance 
to the passage of liquids and the solutions gained entry between the 
cuticular membranes from the glandular group of cells. 
The writer is of the opinion that the phenomena discussed justify the 
conclusion that the micropyle is the point of rapid entry and the seat of 
differential action through the agency of the embryonic appendage, whilst 
slow differential filtration takes place across the chalazal tissue lying along 
the furrow. 
Conclusions. 
From the evidence collected in the present paper it is concluded that: 
1. Only a small part of the water absorbed by the 'grain of barley 
when steeped in various solutions enters by the general surface of the grain, 
which is invested by three layers of cuticularized cell-wall. 
2. Special spots for the entry of water occur in the germinal region 
