Sunshine, Rain, and Wind 



On Cologne Cathedral one can see rosebushes and 

 privets which have been there established by birds.^ 

 On many stone bridges one may find tiny plants of the 

 black maidenhair, which are not to be discovered any- 

 where else within several miles. Other cases are the 

 well-known alga of the snow, and the curious gossamer- 

 like snow-mould, which seems to be only found on 

 decaying vegetable matter in the hollow formed by a 

 thaw between the snow and the earth.^ 



There are certain plants in the Amazons which only 

 occur in the <* gardens " formed by intelligent ants and 

 so on. Such examples show how ingenious plants may 

 be in adapting themselves to the strangest existences. 



In order to live under such special and peculiar 

 conditions, great changes are required not only in 

 the outward form of leaves, stems, and roots, but also 

 in microscopic structure. The peculiarities of desert 

 plants and water plants belong rather to the botany of 

 ten years ago, and have been thoroughly studied by 

 Henslow and many others.^ 



There are two different methods which have been 

 used by various botanists of late years in the study of 

 environment. One may take one particular genus, say 

 the oak tree, and study the leaves of every species of 

 Quercus in the world in connection with the various 

 climates in which those species are found."^ Or one 

 may take some particular kind of habitat or climate and 

 distinguish the type or types of leaf that seems to pre- 

 dominate under those special conditions. 



The great work of Dr. Hansgirg on the shapes of 

 leaves is an instance of this last method. As no one 

 has ever studied leaves with the same thoroughness and 

 wide experience, he has certainly earned the right to 

 generalise, and his conclusions are therefore of great 

 importance. According to him, the object of every 



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