54 RHODODENDRONS AND OTHERS 



their leaves tightly into pencils at the first touch of 

 frost ; whereas R. Indicum, ciliatum, glaucum, hirsu- 

 tum, and ferrugineum do not alter the position or 

 arrangement of their leaves with the mercury at 18 

 Fahr. 



No idiosyncrasy in most Ericaceous plants, especially 

 in rhododendrons, has been more generally recognised 

 than their refusal to grow in soil containing lime. 

 Hence when Mr. Wilson and Mr. Forrest first described 

 how they had found in Western China several species 

 of rhododendron not only flourishing in fissures ot 

 limestone rock, but actually rooted in screes consisting 

 wholly of limestone debris, their reports were received 

 in this country with much surprise, and even, let it be 

 confessed, with some incredulity. But the evidence of 

 two such experienced and trustworthy witnesses could 

 not be seriously doubted or set aside. Subsequent 

 research and experiment have amply confirmed their 

 observation. It has long been known that the roots of 

 certain, probably all, plants of the Heath order, have 

 their roots closely covered and penetrated by a fungus 

 which acts as feeder to its host. The common ling or 

 heather, for instance, is incapable of drawing nutriment 

 from the soil except through the ministration of its 

 humble messmate. So it is with rhododendrons ; if the 

 fungus sickens, so does its lordly host ; if it perishes, 

 the rhododendron is doomed to death by starvation. 

 It appears, therefore, that the inability of rhododendrons 

 to grow in a limey or chalky soil must be traced to the 

 fact that such soil is fatal to the fungus. How, then, 

 can some species of rhododendron nourish in China 



