THE DESCENDING- SAP 



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FIG. 182. TREE-DESTROYING MUSHROOMS. 



Their rhizomorphs or mycelia ascend the tree beneath the bark and cause destruction of its tissues. The species 

 represented are the Sulphur-tuft (Hypholoma fasciculare) and the Honey-coloured Mushroom (Armillaria mellea). 



of nothing but lustreless earth and yellowish grey fragments of stone, 

 dotted over with tiny, dull green, feather-like Moss-plants (fig. 178), as well 

 as with multitudes of delicate branching threads, which are simply more 

 Moss-plantSj but in an earlier stage of development. It is from, these slender 

 filaments or, rather, from the spherical and microscopic cells at the ends 

 of their branches that these deceptive and beautiful scintillations arise. 

 In fact, the little semi-transparent globes, each of which contains a few 

 grains of chlorophyll, act like the lenses of a cat's eye, refracting the 

 scanty incident light where it strikes the globes, and producing a bright 

 disc on each as the result (fig. 179). By this means the light is concen- 

 trated on those places where the chlorophyll is situated, and, in spite of 

 the surrounding gloom, the granules are able to discharge their special 

 functions in an entirely efficient manner. The name of this very curious 

 luminous Moss is Schistostega osmundacea. 



There are other Mosses (e.g. Hookeria splendens) which exhibit the same 

 phenomenon, though in a less marked degree ; nor are these special 

 organizations confined to the Musci. They are to be found in many of the 

 Sea-wracks and other submarine plants ; though the deep-sea Algse are more 

 often distinguished by an optical phenomenon of another kind. The popular 

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