Apbil 2, 1915] 



SCIENCE 



483 



parasite or saprophyte its life history must 

 be known. 



Here is a vast field for investigation 

 which offers great opportunities for mak- 

 ing valuable contributions to knowledge. 

 Thousands of pleomorphic species whose life 

 histories are unknown await the patient 

 and properly equipped investigator. Pres- 

 ent culture methods must be improved and 

 new methods probably devised in order to 

 induce many of these fungi to pass through 

 their complete life cycles. It is in this 

 field that we may expect very important 

 discoveries in regard to the factors which 

 determine the production of any particular 

 spore form in the life cycle of a fungus. 

 Of such factors we have very little definite 

 knowledge at present. 



PARASITISM 



The exact nature of parasitism, its origin 

 and modifications, is naturally of the ut- 

 most significance to pathology. This prob- 

 lem can perhaps be attacked with the great- 

 est promise of successful solution in those 

 cases which appear to be near the border 

 line between saprophytic and the parasitic 

 species. If we admit that evolutionary 

 processes are still active, there seems no 

 reason to doubt that parasites are at pres- 

 ent in process of evolution. Whether this 

 evolution is brought about by mutation or 

 by a gradual accumulation of slight varia- 

 tions or by some other process or complex 

 of processes not yet discovered, it would 

 seem possible to get further light on this 

 subject by a thorough investigation and 

 comparison of some of the active parasitic 

 Ascomycetes and their near relatives which 

 seem to be saprophytic or only very weakly 

 parasitic. A striking example of this con- 

 dition of affairs is presented by the genus 

 Endothia already referred to. EndotMa 

 parasitica is a most virulent parasite, 

 whereas its near relative, E. radicalis, 



which occurs on the same host, shows little 

 or no parasitic tendencies, while some of 

 the other species show slight indications of 

 parasitism. 



ECOLOGY 



In this connection it may be well to call 

 attention to the great possibilities in the 

 study of the ecology of the fungi. At 

 present, unfortunately, there is little ex- 

 act knowledge of the distribution and en- 

 vironmental relations of fungi. The exact 

 limits of , distribution of but very few 

 species is known, and in fact the exact 

 identity of many species is stiU doubtful. 

 The question of their host relations is alsa 

 not well understood except in the case of 

 the rusts, smuts and powdery mildews. 

 Our studies of EndotMa appear to indicate 

 that, in this group at least, the species have 

 very definite geographical ranges which 

 are not determined by their host relations, 

 but apparently are very intimately asso- 

 ciated with climatic and other environ- 

 mental conditions, as well as competition 

 with other fungi. All these things are of 

 vital interest to the pathologist, especially 

 in connection with the possibilities in the 

 way of the spread of any particular para- 

 site, or in determining the probable be- 

 havior of any foreign species which might 

 be introduced. To know what fungi exist 

 in any region and what their natural dis- 

 tribution and host relations are, is of the 

 utmost importance in devising ways and 

 means to prevent their introduction into 

 other countries. In this connection I may 

 quote from Winthrop Sargent in the Final 

 Report of the Pennsylvania Chestnut Tree 

 Blight Commission, 1914, page 12, as he 

 presents the case in a very plain and force- 

 ful manner: 



In. eonelusion, it seems necessary to call sharp 

 attention to the real lesson to be learned froiQ the 

 chestnut blight epidemic — viz. : the necessity of 

 more scientific research upon problems of this 



