THE SCOURING-RUSHES. 



the stem, besides a series of small oval vallccular canals 

 alternating with a series of still smaller carinal canals in 

 the thin walh. Externally the stem bears from twenty 

 to thirty or more narrow longitudinal grooves, the ridges 

 between them being covered with many minute cross- 

 bands of silex. Occasionally these bands break- 

 down in the centre, leaving a double row of 

 silicious tubercles. The amount of silex in the 

 outer coat varies, but usually it so completely 

 covers the epidermis that the vegetable matter 

 can be dissolved out by acids, leaving a com- 

 plete outline of the stem in silex, a sort of 

 stone or glass skeleton. 



The scouring-rush fruits in a yellowish, cone- 

 like catkin at the apex of the stem. Occasion- 

 ally, during the second summer, small cones 

 may be produced at the tips of the short 

 branches also. The terminal cone is ovate, 

 about half an inch long, and ends in a short 

 hard point. The principal fruiting-season is in 

 May and June, though the cones, usually small 

 and undeveloped, may be found at any time, 

 and the plant fruits in a desultory way until 

 October. Even in winter the compact little 

 cones have fully-formed spores packed snugly 

 away until a more propitious season. If one 

 of these winter cones be split from tip to base 

 with a sharp knife, and the cut surface be 

 quickly examined with a lens, a most interest- 

 be revealed. From the gaps 

 made in the delicate walls of the spore-cases, 

 a lively crowd of spores come tumbling out, 

 jostling one another in their haste and apparently 



SCOURING * n * s ig nt 

 RUSH. 



kquisetmn 



