482 



SCIENCE 



[N. S. Vol. XLI. No. 1057 



ing number of the species and the few 

 workers made it impossible for them to 

 devote the time and study to the organisms 

 necessary for satisfactory segregation and 

 description. Species were usually based 

 upon supposed host relations, slight morpho- 

 logical differences or geographical distri- 

 bution. More recent and thorough studies 

 have shown that these can not be generally 

 depended upon. While one species of a 

 genus may have very definite host relations, 

 the next one may be very indefinite in this 

 respect. In the same way morphological 

 characters which are reliable in one genus 

 or species may be very variable and unre- 

 liable in another. The same may be said 

 of geographical distribution. Some species 

 are apparently more or less cosmopolitan, 

 while others are confined to rather limited 

 geographical areas. These facts can only 

 be determined by the most thorough mono- 

 graphic study of each genus or group. Our 

 studies of Endothia have brought out these 

 points with great clearness and emphasis. 

 For instance, one of our American species, 

 E. gyrosa, extends from the Atlantic coast 

 to the Pacific, and from Connecticut and 

 Michigan to Florida and Texas, whereas 

 its near relative, E. radicalis, is restricted 

 to the Appalachian region in America. 

 Such facts are of exceeding importance to 

 the pathologist in determining the nature 

 and possibilities of a parasite. 



LIFE HISTORIES 



Of still greater importance to pathology, 

 however, is a knowledge of the life his- 

 tories of parasites. This subject is not 

 only of exceeding importance to pathology, 

 but also to phylogeny and taxonomy in 

 general, and has important bearings on all 

 other branches of mycology. The work of 

 Tulasne and De Bary and their contempo- 

 raries was the first important contribution 

 to this subject. Following the discovery 



of the pleomorphy of the Ascomycetes there 

 was a tendency on the part of some mycol- 

 ogists to connect up all the various known 

 forms of the so-called Fungi Imperfecti 

 upon the basis of association, similarity or 

 other more or less uncertain evidence. One 

 of the most striking cases of this is fur- 

 nished by Fuckel in his "Symbols Myco- 

 logies," 1869, where supposed pycnidial 

 or conidial forms are given for the ma- 

 jority of the Ascomycetes listed. In some 

 cases the author was probably correct, but 

 none can be accepted without being veri- 

 fied by cultural studies or other reliable 

 methods. The work of Tulasne, while much 

 more reliable and satisfactory, was based 

 primarily upon the intimate association 

 or union in the same stroma of the differ- 

 ent forms of fructification. Much of his 

 work has already been verified by later in- 

 vestigators. Brefeld in his great work on 

 the life histories of the fungi made an ex- 

 ceedingly important contribution to this 

 subject. Unfortunately, many of the coni- 

 dial and pycnidial forms which he obtained 

 in culture from ascospores can not be iden- 

 tified and connected with certainty with 

 forms already described. 



It has already been thoroughly demon- 

 strated that some of the Pyrenomyeetes 

 have from one to three metagenetic spore 

 forms besides ascospores; e. g., Sphcerella, 

 Glomerella, Guignardia, Plowrightia, etc. 

 It is also well known that some of the 

 stages of a fungus may be parasitic and 

 others apparently saprophytic; e. g., many 

 Pyrenomyeetes mature their perithecia 

 upon dead vegetable matter, while their 

 pycnidial or conidial forms may be actively 

 parasitic. This has led to the classification 

 of most of the Pyrenomyeetes, whose life 

 histories are not known, as saprophytes. 

 It is clear, therefore, that to even be able 

 to classify an organism satisfactorily as a 



