698 



SCIENCE. 



[N. S. Vol. V. No. 122; 



(individualismus). While there are a number 

 of lichenologists at the present day who accept 

 this theory of the lichen, which has been elabo- 

 rated farther by Keinke, it should be understood 

 that there are others who are not convinced 

 by the ' relentless ' logic which separates the 

 lichen fungi as a distinct class, but who look 

 upon this relation of fungus and alga as para- 

 sitism in which the fungus is no more depend- 

 ent on the alga than are certain other fungi upon 

 their hosts. In the perennial parasitic Bxo- 

 ascese, for example, the affected parts of the host 

 in the case of such species as Exoascus deformans, 

 E. pruni, etc. , are totally unlike the normal parts 

 of the host, and during their existence, in 'form, 

 necessities and mode of life, differ completely 

 from either of their components.' This de- 

 formed structure differs from the lichen only in 

 the fact that the entire host is not a changed 

 and ' new ' being. But here there is no neces- 

 sity for this, since the host is a bulky, m.ulti- 

 cellular structure, while the alga which is asso- 

 ciated with the fungus is often an unicellular 

 organism, or one of a few cells, or at most in a 

 few cases a comparatively complex organism of 

 small size, so that it could not afford a suffi- 

 cient amount of nutrition for the fungus unless 

 woven in close connection with the fungus 

 threads. 



The author recognizes that the same kind of 

 ' individuation ' which is manifested in the 

 lichens also exists in the modified structure 

 brought about by the parasitism of many of the 

 fungi when he cites the negative geotropism 

 characteristic of witches' brooms, since the new 

 growth is no longer controlled by the same laws 

 of growth as the normal lateral branches. Fur- 

 ther, he points out that this structure possesses 

 other characteristics not exhibited by normal 

 plants when the witches' broom of the silver fir 

 casts its needles each year. In other cases they 

 bear no flowers or fruit. ' ' From these facts it 

 can be deduced that parts of plants attacked by 

 fungi exhibit that kind of symbiosis with the 

 fungus which we call individuation, the joint 

 community behaving more or less as a parasite 

 on the stem or branches of the host plant. This 

 is clearly the case where the attacked parts 

 exhibit increased growth, and at the same time 

 a diminished production of chlorophyll result- 



ing from degeneration of chloroplasts. Such 

 parts of plants are quite as individualized as- 

 the lichens, with the single distinction that they 

 remain in communication with the parent plant 

 and draw nourishment from it." 



From this it would seem reasonable to con- 

 clude that if the fungi which attack algse are to 

 be placed in a separate class because of this in- 

 dividualized condition, as some contend, these 

 ' individualized ' parts of vascular plants should 

 be separated as another class of organisms. We 

 do not understand, however, from his discus- 

 sion that the author sanctions the separation of 

 the lichen fungus from other fungi as a distinct 

 class rather than on the ground of convenience. 

 It has been a matter of convenience as well as 

 one of taste to study and publish the lichens 

 separately, just as it is often a matter of con- 

 venience to separate the parasitic fungi from 

 others. But neither matters of convenience, nor 

 taste, nor continued dependence upon some other 

 organism and physiological amalgamation with 

 it for limited periods, should be the ruling princi- 

 ple in natui-al taxonomy. 



The word ' individuation ' (individualismus)- 

 is misleading, unless the author means by it that 

 the lichen has become a being with individual 

 traits as distinct as those beings which are rec- 

 ognized as individuals. If this latter interpre- 

 tation is given it would seem to violate one of 

 the fundamental criteria of an individual being, 

 namely, that in reproduction it must pass 

 through the one-cell stage, while the lichen 

 thallus is never originated by less than two cells. 

 The author uses the term nutricism to denote 

 the ' symbiotic ' relation of ' mycorhiza ' to- 

 their hosts, as exampled in the case of Mono- 

 tropa and the filamentous fungus covering its 

 roots, the mycodomatia of the alder, the leg- 

 umes, orchids, etc. These general topics make 

 up the first part of the book aiid cover about 

 100 pages. 



The second part covers over 400 pages and 

 treats first of the pathogenic fungi and lastly of 

 the pathogenic algse. 



The fungi are taken up in the following 

 order : Chytridiaccfe, Zygomycetes, Oomycetes, 

 Ascomycetes, Ustilagihefe, Uredinese, Basidio- 

 mycetes. Then follow the ' Fungi Imperfecti.' 

 The discussion of each genus is preceded by a 



