Evolution of Plants 329 



derived all along the scale of plant life by degradation change 

 from autotrophic plants, such a view has considerable in its 

 favor. Then it might be claimed that from an emerald-colored 

 chlorophyll slow degradation changes through greenish yellow 

 to yellow-pink, pink-white, and finally to white took place. 

 In the process also transition might conceivably have been 

 made from the decidedly specialized mode of chlorophyll 

 elaboration to the simpler one of sulphur or iron energizing 

 action. 



Against such a view should be placed the fact that para- 

 sitism or saprophytism, even amongst fungi and higher plants, 

 always leads to a dependence on increasingly rich sources of 

 organic food, not on comparatively simple inorganic material. 

 It seems quite probable therefore that the sulphur, iron, and 

 siliceous bacterial organisms represent the most ancient and 

 the simplest existing types of life, from which or from nearly 

 related types others have been slowly derived. 



But as plant life increased in quantity, and steadily under- 

 went decay, derivative species and genera of colorless bacterial 

 organisms may have evolved, which biochemically slowly 

 adapted themselves to a saprophytic, next to a facultative 

 epibiotic, and finally to a holoepibiotic life.* But even to 

 judge from examples of Blue-green Algse now living, such as 

 species of Dichothrix and Calothrix, it seems fairly assured 

 that not a few species passed from a green state to a colorless 

 condition of saprophytism, and still later to a semiparasitic or 

 a parasitic state. 



We may therefore say for the bacteria that the simplest 

 genera consist of a wall enclosing vacuolar or finely foam-like 

 protoplasm in which there may not be, or there may be, dis- 

 tributed chromidia or chromatin granules. Some of these 



* In discussing the possible origin of animals from a primitive plant ancestry, 

 it is important to distinguish between attaching parasitism and the ve^j;>' dif- 

 ferent relation where a free colorless organism moves actively in search of 

 food. The former state seems always to be associated with advancing degen- 

 eration, and to it strictly the term "parasitic" should alone be applied. The 

 term "epibiotic" may then be used in connection with colorless organisms that 

 move freely in search of, and live directly on, fresh plant or animal tissues, and 

 epibiotism as the condition. 



n* 



