THE PROTOPLAST AS HOUSE-BUILDER 



69 



but just above it is so abundant that further progress of the mycelium is 

 stayed. The Spruce and Weymouth Pine are not so rich in resin, and up 

 their trunks the mycelium of the deadly Forties annosus spreads rapidly, 

 causing the condition known as red rot. 



Wax is another frequent vegetable production, especially in the torrid 

 zone, where many of the wax-bearing plants supply the natives with light. 

 This substance gives the bloom to the plum, cherry, and grape ; and " the 

 raindrops lie on the waxy surface of the Cabbage-leaf like balls of diamond, 

 from the total reflection of light at their points of contact." Wax is secreted 

 in the cuticle for the purpose of getting rid as rapidly as possible of the 

 water which is deposited on the surfaces of the leaves, or to prevent exces- 

 sive loss of water by transpiration the latter an invaluable provision 

 in the Aloe, Cactus, and other fleshy leaved plants inhabiting the hot, 

 parched regions of the tropics. A further use is noticed by Kerner. He 

 tells us that the branches of many Willows which bear honey-laden flower 

 catkins are provided with wax-like coverings (combinations of fatty acids 

 with glycerine), so extremely smooth and slippery that would-be visitors to 

 the flowers (unserviceable, honey-thieving ants for the most part) strive in 

 vain to accomplish the ascent. 



The delicate waxen bloom of many plants presents some curious forms 

 under the microscope. The bloom on the Rye, familiarised in a once popular 



Photo by] 



FIG. 98. PINE FUNGUS (Pomes annosus). 



[E. Step. 



This fungus attacks Pine-trees chiefly through injured roots, and spreads thence up the trunk. The Scots Pine has an 

 abundant store of resin just above the roots which prevents the upward progress of the fungus. It is the cause of 



" red rot." 



