LABORATORY STUDU-.S 265 



and examine it, using a low power. Note the sac-shaped spore 

 cases upon the under side of the leaf. JMount 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 elatcrs; 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) ]\Iake ver}^ 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. 



(/) 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 C.ALAMOPHYTA 



The same as for the preceding jihylum, and 

 M. C. Stopes, Ancient Plants, London, 1910. 



