EVOLUTION BY DEGENERATION. 



23 



Alpine and Arctic Degradations. — Mountain plants of the higher 

 and drier zones cease to be able to grow tall, and exist as dwarfs ; 

 consequently so many form excellent rock-plants for gardens, as the 

 flowers of high alpine plants are often more brilliantly coloured than 

 those of the lowlands. Beyond the tree-zone, some trees manage to 

 reach high latitudes, but they cannot grow beyond i to 3 or 4 feet, as 

 the Norway Spruce and the dwarf Birch, which is about i foot in 

 height. 



If we turn to any flora, we find the systematic botanist takes all 

 the features mentioned as specific or generic characters, because 

 they are constant ; and the plants cannot be otherwise characterized 

 and recognizable by the student who wishes to study plants and 

 compare them with the descriptions given; yet those very features 

 are simply the result of varying degrees of impoverishment and 

 degeneracy. 



Degradations through Parasitism and Saprophytism. — One of the 

 most characteristic examples of degeneracy is seen in parasitic and 

 saprophytic plants, which live upon others or on decayed organic 

 matter, respectively. Typical examples of such plants have no green 

 leaves or stems. The cause of their absence is the fact that they 

 do not require them ; since all plants which live in the earth derive 

 the main source of their tissues — carbon — from the carbonic acid gas 

 of the atmosphere. This is absorbed and the carbon taken to form 

 starch, the first visible result of such food. Since, however, the " host- 

 plants " of parasites can supply it, as also does decayed vegetable 

 matter for saprophytes, parasites and saprophytes become degenerate 

 plants in this respect, and develop no chlorophyll, which makes leaves 

 and shoots green. 



The family of Broomrapes [Orohanche) and the Dodder — a member 

 of the Convolvulus family — are familiar parasites. Some orchids, as 

 the Bird's-nest Orchis {Neottia Nidus-avis) and the rare Coral-root 

 Orchis (Corallorhiza innata), are saprophytes as well as the Bird's-nest 

 {Hypopithys multiflora) allied to the Heath family. 



In all these the leaves are represented by white or somewhat 

 coloured scales, and, of course, supply the systematic botanists with 

 specific and generic characters. 



Thus is it that the evolution of plants proceeds in two directions ; 

 but whatever they may be, it is always the result of self-adaptation 

 to the conditions of life, or, as Darwin expresses it in his alternative 

 to the theory of " Natural Selection," they are the " results of the 

 direct action of changed conditions of Ufe, without the aid or means 

 of Natural Selection." 



