of some Phanerogamic Parasites. 307 
relations to the cells which they attack, than do the more 
solid host-plants of C. americana which are at hand. That 
these relations are the same in both parasites will be shown 
further on. C. glomerata , like C americana , strikes its 
haustoria into the leaves as well as into the branches of its 
host. The tissue of the leaf of Impatiens Balsamina is still 
more spongy than that of the stem, and in its loose 
parenchyma the bundles are rather widely separated. A 
haustorium which strikes into a leaf is less compact than one 
which penetrates a branch. The cells of the sucker, instead 
of growing as a cone straight forward, spread out into a 
brush-form. Some of those at the sides of the brush grow 
for some distance into the spongy mesophyll ; the others 
unite ultimately with a fibro-vascular bundle. Fig. 15 shows 
the tip of a haustorium growing towards a bundle. The 
large, thin-walled, papillate cells dissolve the walls of the 
cells with which they come into contact, making perforations 
little larger than their own diameter. The walls of the 
parenchyma-cells are entirely dissolved only when enough 
haustorial cells intrude to occupy their whole diameter. The 
haustorial cells, as the figure shows, do not all grow at the 
same rate ; hence the solution of the walls of opposing cells 
is a gradual process accomplished by several haustorial cells 
one after another. The contents of the opposing cells are 
dissolved rather slowly by the cells of the sucker, the starchy 
substances first, the protoplasmic later. The haustorial 
cells exercise little or no pressure, growing forward in the 
path which they have dissolved for themselves. Since the 
diameter of the haustorium is nearly the same from a point 
near its tip to its base, it occupies little more space than has 
been cleared for it by the solvent action of the cells of the 
sucker. Some of the cells of the sucker grow faster than 
others, and some, particularly at the sides, grow out in 
directions in which their neighbours do not follow. Some of 
these may penetrate more than one parenchyma-cell, growing 
straight through from side to side, dissolving a passage 
through walls and contents little if any larger than their own 
