BARBER: CERTAIN CRYPTOGAMIC PLANT MATERIAL. I1l3 
among the best kinds of insects to use, and they are allowed to 
sink until they rest on the water plants beneath the surface. It is, 
of course, advisable to have the water free from animals which 
may eat the insects. 
It is often desirable to demonstrate to large classes the methods 
by which spores are scattered in mosses, ferns, Equisetums and 
other plants in which hygroscopic action is observed. For this 
purpose the stereopticon has been used in the following way: 
Rather thick sections are made through the fruiting parts where 
ferns and Equisetums are used. ‘These are mounted in water on a 
slip without a cover, the surplus water is drawn off and the prepa- 
ration is placed in the ordinary apparatus for projecting objects on 
the screen. ‘The heat from the source of light causes the water to 
dry rapidly, and just at the moment of drying the characteristic 
movements of the annuli and elaters may be seen projected on the 
screen. The addition of moisture will cause the hygroscopic parts 
to resume their former position; in the case of Equisetum, breath- 
ing on the side is sufficient. To observe the action of the peristome 
of moss capsules the whole capsule is mounted. 
More exact inethods are doubtless often more useful in investi- 
gation, and other ways of applying the ones given above may sug- 
gest themselves to teachers. These, however, have been found 
very helpful in teaching, especially in classes of beginners; and in 
the form given above have proved successful under the conditions 
present. 
