= 
ai 
LABORATORY STUDIES 265 
and examine it, using a low power. Note the sac-shaped spore 
cases upon the under side of the leaf. Mount some of the spores 
dry, using no cover-glass, and examine with the 16 mm. 
objective. Breathe upon the spores very gently to moisten 
them, and notice the coiling of the elaters; observe the quick 
uncoiling which takes place upon the evaporation of the 
moisture. 
(c) Sow a quantity of the fresh spores upon moist earth or 
porous pottery, covering with a bell-jar and taking every pre- 
caution to secure constant moisture. The spores will begin to 
germinate in a few days, when studies of successive stages of 
growth may be taken up. By care the mature gametophytes 
(prothallia) may be grown, and the antherids and archegones 
studied. 
(d) Make very thin cross-sections of the stem of the Common 
Horsetail. Note the position of the vascular bundles. Now 
make a vertical section of the bundles and study the tissues, 
using high powers. 
(e) Study the breathing-pores on the green stems of the Com- 
mon Horsetail. Compare these with those of the Scouring 
~ Rush. Study also the disposition of the chlorophyll-bearing 
tissue in cross-sections of both stems. 
(f) Examine underground stems of Horsetails, and compare 
the structure with that of the aerial stems. Make cross-sec- 
tions of the roots which are attached to these underground 
_ stems. 
LITERATURE OF CALAMOPHYTA 
The same as for the preceding phylum, and 
* M. C. Stops, Ancient Plants, London, 1910. 
