GENERAL CLASSIFICATION 95 



Tavel, F. von. Vergleichende Morphologie der Pilze. 208 pp. go Jigs. 1892. 

 Tulasxe, L. R. et C. Selecta Fungorum Carpologia. (In 3 vols.) 782 pp. 



64 pis. 1861-1865. 

 Underwood, L. M. Molds, Mildews, and Mushrooms. 214 pp. 9 pis- 1899. 

 Zopf, W. Die Pilze. 500 pp. 163 Jigs. 1898. 



Every great division, or class, of the fungi contains some spe- 

 cies capable of producing disease in other plants. Disease, in this 

 connection, refers to a physiological disturbance, often accom- 

 panied by anatomical injuries or hypertrophies. The number of 

 such disease-producing organisms is sometimes very limited in a 

 class, and there are orders in which no such organisms have been 

 described. 



In a restricted sense the fungi may include only certain classes 

 of chlorophyll-free thallophytes, but in the broader application of 

 the term, it includes all chlorophyll-free organisms which may be 

 regarded as plants. It is with this latter meaning that the term is 

 here used, in so far as the general selection and arrangement of 

 material is concerned, although this will not be permitted to affect 

 the use of the word in a restricted sense as well. The fungi in- 

 clude five well-marked classes of organisms, as follows : 



1. Myxomycetes. The slime molds. 



2. Scliizomycctes. The bacteria. 



3. Phycomycetcs. Water molds, black molds, downy mildews, 

 etc., — algal-like fungi. 



4. Ascomycetes. The ascus-bearing fungi. 



5. Basidiomycetes. Basidia-bearing fungi, — smuts, rusts, mush- 

 rooms, etc. 



This grouping, however, shall not be taken to indicate a line of 

 development beginning with the slime molds and advancing through 

 the other groups to the smut and mushroom class. In fact, only 

 the Phycomycetes, Ascomycetes, and Basidiomycetes, which have 

 much in common, may be regarded as the true fungi, and nearly 

 all the species here included have a filamentous vegetative stage. 

 The bacteria form a coherent, distinct class, yet certain families 

 show very close relationship with the fungi, while others show more 

 striking resemblances to certain families of algae. The bacteria 

 have, moreover, in no sense any very close animal-like allies. The 

 Myxomycetes have no very apparent relationship with any other 



