296 Peirce. — On the Structure of the Hans tor ia 
made by the cushion-cells, carrying with it along its sides for 
a short distance into the host some of the cortical and epi- 
dermal cells which overlaid it. It completely fills this opening, 
enlarging it by solution, and later by pressure, thus soon 
forming around itself a mass of compacted walls of dead cells 
from which all nutritive matters have been removed by 
solution (see Figs. 6 and 7). 
The long cells forming the apex of the haustorium have 
already begun to grow rapidly, their walls, especially at the 
tips, remaining thin. They dissolve their way through the 
cortical tissues of the host, exercising little if any pressure, 
as the absence of collapsed cells in front of them shows. (To 
save useless repetition, the reader is referred to pages 307 and 
308 where the relations of these cells with those of the host 
are discussed in detail in the description of C. glomerata ). Im- 
mediately behind these cells, which have now become papillate, 
and may conveniently be termed collectively the sucker , other 
cells by continued divisions provide for the elongation of the 
haustorium as fast as room is made for it in the host by the 
action of the sucker. 
The subsequent extension of the haustorium varies in 
accordance with the structure of the host. If the host be 
a plant similar in structure to the parasite, that is, with 
a single ring of open collateral bundles separated by con- 
siderable masses of parenchyma, the haustorium grows 
generally through the cortical into the interfascicular paren- 
chyma. If the fibro-vascular bundles are widely separated 
by parenchyma, the haustorium approaches and applies itself 
laterally to the bundle nearest to it. If the scattered 
bundles are not far apart, so that the haustorium occupies 
nearly all the space between them, it grows laterally more 
rapidly than in the apical direction, and so applies itself to 
both bundles (see Fig. 6). This is the case in one of the 
Mimoseae studied. Having applied itself to one or both of 
the bundles between which it grows, the haustorium grows 
but slowly at its tip, continuing however to extend itself 
for a greater or less distance into the pith. If the host 
