354 ECOLOGY 



other trees and shrubs, and the ground flora is very 

 scanty (Fig. 190). The more common trees are 

 Gean (Prunus avium) and Yew ; the latter some- 

 times forms a shrub layer, as do the Hazel and Holly 

 in Ash and Oak woods. The characteristic species 

 of the ground flora, especially in the lighter parts, 

 are Dog's Mercury, Sanicle, Violets (V. sylvestris, 

 V. Riviniana, and V. hirta), Strawberry, Enchanter's 

 Nightshade, Helleborines, Large Butterfly Orchis, 

 and the saprophytes, Bird's-nest Orchis and the 

 Yellow Bird's-nest (Monotropa) ; also the Green and 

 Stinking Hellebores, Deadly Nightshade, Spurge 

 Laurel, and Butcher's Broom (Ruscus aculeatus). 



CHAPTER XXIX 



PLANT-LIFE IN HUMUS 



Abnormal Modes of Nutrition 



The work of Fungi in humus. The surface layers of the 

 soil contain much organic matter, and are commonly covered 

 by the remains of plants which are the accumulations of 

 successive years of growth. In meadows and pastures, this 

 tangle of vegetable matter, living and dead, forms the 

 turf. In woods, we know it as leaf-mould or humus ; 

 and it is often many inches in thickness. On the moors, 

 it forms deep beds of peat. Examine the leaf-mould in 

 a wood, and, on lifting it from the ground, note that the 

 decaying leaves are often held together by a white, felt- 

 like mass of mould-threads. This felt is the vegetative 

 part of various species of Fungi and is known as the 

 mycelium. From this mycelium arise the fruit-bodies of 

 the Fungi, some of which we are familiar with as Mushrooms 



