308 Peii ce. — On the Structure of the Haustoria 
diameter. One such cell is shown in Fig. 1 6, a , the red 
being the haustorial cell, the black the parenchymatous cells 
through which it has grown. Similar cells are shown in 
cross-section in Fig. 16 b , 1 6 c. These parenchymatous cells 
contain prominent nuclei, abundant protoplasm, and numerous 
chloroplastids. That one haustorial cell robs them of enough 
food to kill them is disproved by the fact that it may pass 
through three or four in its whole length, the contents of 
which are scarcely less than those of other and unattacked 
mesophyll-cells. There are no pathological appearances 
except the presence of the haustorial cell ; both live, and the 
mesophyll-cell is apparently as well off as before it was 
attacked. The explanation is not far to seek. The meso- 
phyll-cell makes and receives more food than it can consume. 
In a healthy leaf the excess of food made over what is 
consumed, is temporarily stored in its tissues, as the deposits 
of starch at certain times show, and this is later transferred to 
other parts of the plant. In those leaves which are penetrated 
by haustoria little if any starch is to be found. Why? 
Various causes perhaps combine to produce this result, but 
among them the haustorial cells must be considered 
important. The haustorial cells draw from the mesophyll in 
which they grow much or all of the starch formed in the 
process of assimilation which is not immediately consumed 
by the mesophyll-cells themselves. Unless too many 
haustorial cells attack the same mesophyll-cell it does not 
suffer sufficient loss to injure it to any apparent degree, but its 
value to the whole plant is greatly reduced or entirely 
destroyed by the intruder. 
The cells of the sucker make their way in similar fashion 
through the parenchymatous tissues of the stem. Occasionally 
one finds a haustorial cell growing through cortical cells 
containing chlorophyll, just as in the mesophyll of a leaf, 
without causing any apparent harm to the cells, their proto- 
plasm and nuclei seeming to thrive in spite of the intruders 
presence. In the interfascicular and pith parenchyma, where 
of course no chlorophyll exists, such does not seem to be the 
