OTHER FERN-LIKE PLANTS: HORSETAILS 



375 



extensive underground stem which is much branched. Upon 



this are formed two kinds of aerial shoots, the 



fertile and sterile shoots. The fertile shoots are 



formed during late summer and autumn, but the 



stem remains short during the winter. Very 



early in the spring the stem elongates, pushes 



above the ground, and the spores are scattered. 



The fertile shoots are devoid of chlorophyll. Fig. 340. 



_. ., , Peltate sporophyll 



The sterile shoots are developed all through the of Equisetum (side 



, . ,_. view), showing spor- 



summer, are much branched and green. I he angia on under side. 



Fig. 34i. 



Spore of Equisetum with 

 elaters coiled up. 



Fig. 342. 



Spore of Equisetum with elaters uncoiled. 



fruiting spike is narrowly cone- 

 shaped and terminates the fertile 

 stem. The spore-bearing leaves 

 (sporophylls) are peculiar, being 

 shield-shaped with a short stalk 

 which attaches them to the stem. 

 They are in crowded circles around 

 the stem, and thus are angular 

 where they fit against one another. 

 Several sac-like spore cases (spor- 

 angia) are attached to the inner 

 face around the short stalk. At 

 maturity the axis of the cone 

 elongates, the spore cases crack 

 open, and the spores escape. The 



Male and fema^gamete plants of ? w/- Spores have a Very thick Wall. 



&LPff+* The outer layer splits into four 

 tne W rmhSum, C ' s hS thin bands which are attached to 



Fig. 343. 



