' ' DEFENCE, NO T DEFIANCE. '' 



131 



still worse species is the better known " Couch-grass " 

 {Triticinn repens)^ pest to farmers, for its leaves are 

 innutritious and produce scour in 

 cattle ; and the plant can propa- 

 gate itself by the nodes of its 

 insidious creeping stems as well as 

 by seeds ; so that cutting it up 

 means helping it to multiply ! 

 The " Prairie -grass " now trans- 

 ferred to grace our shrubberies, 

 with its drooping blades and hand- 

 some white floral panicles, contains 

 so much silica that its leaves cut like 

 a razor if drawn rapidly through 

 the hand. 



The needle-shaped leaves of 

 Fir and Pine-trees, and of so many 

 other Coniferae, are also rich in 

 silica, and both their shapes and 

 secretions protect them from 

 browsing mammals and the at- 

 tacks of caterpillars. Perhaps 

 also they are further protected 

 thereby from the devastations of 

 parasitic fungi, as few species are fig. 51. — Waii Barky 



, r^ • r T 1 1 1 {Hordeicvt jnurbium'), 



known on Coniierae. it should showing defensive 

 be further remembered that the "beard. 

 Coniferae are the oldest, geologically speaking, of all 

 woody trees ; just as the Grasses are perhaps the 



