PTElilDOPUTTA. 199 



In ancient geological times the Calamites and tlieir allies consti- 

 tuted a distinct order (Calamariese) of tree-like plants f metre in thick- 

 ness and ten metres in height. 



Practical Studies. — (a) Collect in early spring a number of cone- 

 bearing stems of the Common Horsetail. Note the joints (nodes), 

 bearing whorls of united flat leaves, and the cone, composed of whorls 

 of shield-shaped leaves. Split the cone and stem and note that the 

 latter is hollow, with closed nodes. 



(6) Carefully dissect out a single shield-shaped leaf from the cone, 

 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 ^-inch objective. Breathe upon 

 the spores wry gently to moisten them, and notion t|be 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 precaution 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 plants of the first stage (prothallia) may be grown, 

 and the antherids and archegones studied. 



(fl) Make very thin cross-sections of the stem of the Common Horse- 

 tail. Note the position of the flbro- vascular bundles. Now make 

 vertical sections of the bundles and study the tissues, using high 

 powers. 



(e) Study the breathing-pores on the green stems of the Common 

 Horsetail. Compare these with those of the Scouring Bush. 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 crpss-sections of the 

 roots which are attached to these underground stems. 



Class IE. Ytjjicism {the Ferns). 



418. Here the plant-body consists of a solid stem, bearing 

 roots and broadly expanded leaves, the latter usually long- 

 stalked. The stems are mostly horizontal and under- 

 ground, but in some cases they rise to a considerable height 

 vertically in the air. 



