THE SC'DURINCi-RFRHES 



543 



Fig. 370. — Sfouriiig-rusli. A, male gametophyte or pmthallus (>]'•-) show- 

 ing anthcridia (a, a). B-E, spermatozoids of various ages, much 

 more highly magnified. (Hofmeister, Schacht.) 



Fig. .371. — Scouring-rush. Female gametophyte or prothallus (■>,'-) showing 

 arfhegonia (a, a, a) and pseudo-roots {li). (Hofmeister.) 



in a cone-like aggregation of ^-horlecl sac-leaves. Each of 

 these has a stalk ending in a shield-shaped expansion, six- 

 sided from pressure. Behind each angle of the shield is a 

 large sporangium dehiscing by a longitudinal slit (3, 4). 

 The spores are peculiar in having four slender arms which 

 close tightly about the spore when moist, and spread apart 

 in drying, thus serving to eject the spores. Thej' are there- 

 fore called elaters (-5, 6, 7). 



The massive, much-lobed gametophj^te bearing gametangia 

 aljove, and the comparatively large sessile sporangia of the scouring- 

 riislies, indicate a closer kinship with the adder-tongues than with 

 the true ferns, and suggest that the Equisetinae may have evolved 

 from Hepaticie somewhat more moss-like perhaps than Anthoceros. 

 They may be characterized as -plants similar to ferns except in haring 



