io6 Peirce. — A Contribution to the 
a small quantity of water and cast into rods of about six 
centimetres length and less than one centimetre diameter. 
These may be sterilized just before using by soaking for 
fifteen minutes in ether and then rapidly evaporating under 
diminished atmospheric pressure. Into a moist chamber 
made of large glass-tubing, such as I have previously described 
(page 75), which has been thoroughly sterilized, insert the 
irritable tip of a branch of C. glomerata , and by sterilized 
forceps place the rod of plaster and starch in the chamber and 
in contact with the branch, quickly closing the chamber. In 
the course of six days the branch should have twined and 
developed several haustoria. Cutting the branch from its 
parent, remove it, still in contact with the rod, from the 
chamber. By a clean flat-pointed needle remove some of the 
starch and plaster from directly under a haustorium and 
examine it in water under a microscope. With another clean 
flat needle remove some of the starch and plaster from some 
part of the periphery of the rod far removed from any 
haustoria, and examine it also in water. It will be noticed 
that on the first slide, of material from under a haustorium, 
the proportion of starch to plaster is smaller than in the 
original mixture, and that most of the starch-grains still to be 
found are corroded in various degrees (see PI. VIII, Fig. 6). 
The corrosion proceeds in the majority from the centre of the 
grain toward the periphery, forming broad and more or less 
radial canals ; but a very considerable number of grains show 
the corrosion beginning at the periphery and running in, or 
beginning at several points between periphery and centre. 
In the last case, the corrosion proceeds from several centres 
instead of from one, but finally a common cavity is made by 
their union in the centre of the grain. Examination of the 
second slide, of material far from the influence of haustoria, 
will show that the proportion of starch to plaster is approxi- 
mately the same as that of the original mixture 1 , and that 
none of the starch-grains are corroded. 
1 It is scarcely to be expected that the ingredients should have been so perfectly 
mixed that their proportions would not vary somewhat in different parts of the rod. 
