112 PLANT-LIFE 



fruit the basidia, with their spores, are exposed to the 

 air. In the Gasteromycetes the hymenium is protected 

 by a membrane until the spores are mature. If we make 

 a section of a young Puffball, we may note a central 

 cellular, soft, white mass, surrounded by a thin skin. 

 At a later stage small chambers appear in the central 

 mass, and in the walls of these chambers spore-bearing 

 basidia are developed; later still, the tissues of the mass 

 dissolve, and the spores are found in an evil-smelling, 

 watery mess. Ultimately the moisture evaporates, 

 the outer skin bursts, and the dry spores are dispersed 

 by the wind or other agency. 



Lichens. 



The Lichens, or Crottles, as they are called in Scot- 

 land, exhibit just about as cunning an arrangement as 

 can be discovered among the many amazing strategies 

 of the plant world. For a long time botanists hardly 

 knew what to make of them, and where to place them; 

 but we now know that a Lichen is not, strictly speaking, 

 an individual plant : it is, practically, a business partner- 

 ship of two plants, one an Alga and the other a Fungus. 

 Now, an Alga requires abundance of moisture, other- 

 wise it cannot develop ; and a Fungus does its vegetative 

 work in the dark, and is extremely delicate; it shrinks 

 from cold and drought; but a Lichen, which is a com- 

 bination of two delicate plants, is about as hardy a 

 structure as we can find in the whole realm of nature. 

 It can endure the greatest extremes of temperature; 

 species growing on rocks at great altitudes pass un- 

 harmed through weeks of keen frost, and are unscathed 



