io Minnesota Plant Diseases. 



described as degeneration. It is a noteworthy fact that such a 

 plant may be very well adapted for obtaining food in its own 

 way, and in this respect may be highly specialized. The wheat- 

 rust, for instance, is very highly organized and is very closely 

 adapted to its own manner of life. The fungi are specialists 

 along certain lines of obtaining food and are in these lines more 

 highly specialized than leaf-green-bearing plants. Plants with 

 such a habit of life do not need the elaborate starch-making 

 machinery of higher plants, as of ferns and flowering plants. 

 It is easier and more economical for fungi to reduce their vege- 

 tative areas and hence to simplify their structure. It is a case 

 of economy on the part of the plant. In general, all plants, 

 whether fungi or flowering plants, when devoid of leaf-green, 

 are efficient specialists in their absorptive methods while at the 

 same time the vegetative area may be comparatively simple. It 

 must therefore be understood that when these plants are called 

 degenerate it is only in this one aspect of vegetative structure 

 that they are correctly so called. In absorptive power and in 

 reproduction they may be fairly complex. 



It is also well known that parasitism in animals also results 

 in degeneration of structure. There are a large number of 

 worms, such as tapeworms and thread worms, numerous insects, 

 such as fleas and bird lice, and even vertebrates, as the hag 

 fishes, which are parasitic in their habits. In all of these cases 

 simplification or degeneration of the animal body results. Or- 

 gans of locomotion, sense organs, digestive tracts are all pro- 

 foundly affected; either very much reduced or lost entirely. 

 Many flowering plants have also adopted either parasitic or 

 saprophytic habits. Familiar examples are found in the dodder 

 and coral-root orchid. The dodder is usually found in swampy 

 places or in clover fields and is a confirmed parasite. It has 

 lost its leaf-green except in very early life and is consequently 

 in later life yellowish in color. The coral-root orchid grows on 

 leaf mold in the deep woods and is a saprophyte in habit ; it has 

 also lost its leaf-green; and its leaves, as in the case of the 

 dodder, are reduced to small scales, useless for starch-making 

 purposes. On the other hand, all parasites and saprophytes, 

 whether plants or animals, have well developed systems of ab- 

 sorption and reproduction. The fungus system of absorption, 



