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Till-: AM ERIC AX X A TUB A LIST [Vol. XLII 



nary soils. They are mostly confined to swampy and 

 other moist soils that contain much decomposing vege- 

 table matter, and to shady positions. It may be suggested 

 that the abundance of disintegrating organic material 

 contained in the soil in which these completely sapro- 

 phytic plants grow furnishes so large a supply of ma- 

 terial which is still useful for assimilation in the 

 production of new organic substance that the entire leaf- 

 function, including the production of chlorophyl, is 

 suspended as being superfluous, and that this habit has 

 become permanent and hereditary. 



Completely symbiotic phenogams live in enforced vital 

 union with a fungus which adheres to and covers its 

 roots, and through which it derives all its soil-subsistence. 

 The roots being entirely enveloped, their normal function 

 is destroyed and the fungus also assumes the office of 

 purveyor of nutriment. As do other fungi, it obtains that 

 food-material from decomposing organic matter in the 

 soil and transfers a portion of it to its consort through 

 their surfaces of contact. Although that food-material, 

 when obtained by the fungus, is partially decomposed, 

 and is received at second hand by the captive phenogam, 

 the latter thrives upon it, and, its above-ground portion 

 being free, the functions of vegetative growth and repro- 

 duction are normally performed. Its leaves, however, are 

 abortive or functionless and never green in color, for 

 completely symbiotic phenogams do not, and do not need 

 to, produce chlorophyl. Their failure to do so is doubt- 

 less a direct result of the condition which is imposed upon 

 its roots by its fungus consort. The vital relations of 

 these strangely modified phenogams with other plants are 

 normal, but their condition with relation to the fungus 

 is apparently that of pitiable captivity. The usurpative 

 control of their nutrition by the fungus suggests that 

 these phenogams did not originate as symbionts by a pre- 

 dilective departure from a self-supporting condition. 

 Partial symbiosis of fungi with phenogams is not uncom- 

 mon and is understood to be, at least in many cases, 

 mutually beneficial, but it has only incidental relevancy in 



