Symbiosis and Saprophytism 



By Daniel Trembly MacDougal 

 [Plates 367-369] 



General Discussion 



It is customary to desii^nate all chlorophylless seed-forming 

 species which have no nutritive connection with other vascular 

 plants as saprophytes, or more exactly, holosaprophytes (allotropic 

 or heterotropic forms according to Pfeffer's classification), and 

 others of similar physiological tendencies as hemisaprophytes 

 (mixotropic forms), without regard to the nutritive unions formed 

 by the roots or absorbing organs in mycorhizas, tubercles and 

 other associations. It is obvious that the term saprophyte, or 

 holosaprophyte should be applied only to those species which de- 

 rive their supply of food from organic products directly without the 

 intervention of the activity of chlorophyll, and unaided by other 

 organisms. In this sense, and it seems to the author to be the 

 only meaning admissible, the holosaprophytes include numerous 

 bacteria and fungi, but so far as present investigations show, only 

 one seed-forming species, Wiillsddaegdia aphylla : Cephalaiitliera 

 Orcgana was erroneously grouped in this class in a previous 

 publication.* 



* An abstract of this discussion of terms was read before the Society for Plant Phys- 

 iology and Morphology, at New York, Dec. 28, 1898, and was published in American 

 Naturalist, for March, 1899 (lo). See also note on same in Science for Feb. 3, 1899, 

 and Botanical Gazette for Feb. and Sept., 1899. 



[Issued October 16.] ( 511 ) 



