Cc. A. BARBER. 25 
in the direction of the sucker, and show a well developed and 
constant collapsed layer in the middle (Plate VIII, fig. 2, 0). 
This nest of cells is apparently little affected by the changes 
which have taken place. They appear to lie in a sort of eddy in 
the conflicting currents of growth around them. As far as can 
be seen, they correspond with the area marked } im fig. 2 of 
Plate VI, and have been dragged inwards and downwards so as 
to occupy a horizontal instead of vertical position. Tf this is the 
case, the cleared cells at d in the same figure would naturally, as 
suggested above, be crushed and persist only as a minor collapsed 
layer, as at b in fig. 2 of Plate VIII. 
The starchy cells of the cortex are well seen. The radially 
arranged cells are, as in Plate VII, cleared of contents both 
outwards and inwards and have a band of densely packed cells in 
the middle. And, in passing, it is remarkable how sharp is the 
line of demarcation between the starch-filled and the clearer cells 
about to be added to the collapsed layers (see end of para. 10). 
The denser layer does not undergo much further change, its cells 
have apparently entered the permanent stage and their walls are 
brown and firm. Such masses of cells, frequently with remnants 
of starch in them, are met with right on till the end of the 
life of the haustorium. 
14. We have now studied the structure of young haustoria 
which have succeeded in penetrating monocotyledon and dicoty- 
ledon roots, and it is hoped have succeeded in bridging over the 
gap in the series before and after penetration. We have seen 
that the zone of clear cells, ending upwards opposite the middle 
of the gland, is traceable into the tissue that is thrust back 
against the collapsed layers by the opening cortical wings of the 
host’s root. The lower part of the collapsed layers, at first 
arising from crushed cells of the clear zone, is afterwards added 
to by cells of the starchy cells outside, which have lost their 
contents. The middle part arises where nucleus joins cortex, 
above the former glandular region, and is formed entirely from 
the outside, that is from cortical cells. These lower and middle 
