2iS IV" i:().NKKIiKM;K I.NTKKN \TI(iNAI,K ItK (.KNKTK.ll K. 



or on and al thc cxpcnse orotlici' ortfanisnis. Tlic inloirclalionsliips lliat liav<> 

 b('(>n dovoloped in Iho organir world llini miihial adaptation bdweon associatcd 

 organisnis aro cxceedingly coniplex and difficnll to classify'. A distinction 

 shonid lie niade bolweon parasilism propcr and certain closcly related types ol' 

 nntrilion, e. g., MiduaUsm. wliere n^ciprocal benefils are enjoyed by tiie asso- 

 ciated organisms (Symbiosis is a form of mutualism where tbere is fusion 

 between the Iwo organisms, bulisby some, used as a synonyni for pai-asitism) : 

 f'nmmpnxnlism, where benefil resnits to one of the associated organisms and no 

 observable injury cornes to tiie otiier : Predalisin, where one organisni destroys 

 anollier ([uicUly or entirely : and Saprnpliylism, where one organisni lives on 

 the dead remains of others. 



The parasites hâve becn elas^illed arcording to varions viewpoiiits. l-dr 

 example, they are listed by the systematisl hy their taxoiiomic rank, Bacleria, 

 Fungi, wilh their subdivisions the Uredineae, Uslilagineae, llyphomyceles, etc., 

 Algae, Phanerogams, or they may be grouped by the organ attackcd, inlo para- 

 sites of the leaf, stem, root or seed; or by the number of hosts, as monoxenous, 

 heteroxenous; or ])y adaptation or necessily. as facultative or oldigate parasites : 

 and in yet other ways-. 



A new classification, and from our standpoint as slndents of Genetics a 

 much more helpfnl one, is herc proposed to be based on the evolulionary deve- 

 lopmenl or dcgree of adaptation to the parasilic existence. Three groups may 

 conveniently be recognized, withoni oxerlooking the lacl thaï there are nnme- 

 rous inlermediate stages. 



A. In which the adaplive relation IjeLween liost and parasite lias reached 

 the higliesl stage of development . Kx. tiie l'redinae, l'st ilagineae, and Erysi- 

 pheae. 



I). Clearly adapted to s|)ocial hosts. Jnil iavored in their development by 

 circumstances Ihat weaken llic vilalily of llie linsl. l-]x. Alh-rnaria Sulnni. 

 Plioina Beldc 



C. LeasI a(lapl('<l lo (lie parasilic exisiriice, usually wound parasites, orteii 

 highly destruclive lo llir lissnes ni' llieii host. Kx. l',iti-iUii>i (■(inilornciix. Blii- 

 zopi/s nigririnix. 



The qualilies wliirh deli'i'iniiie tlie r.'ink (.la ]iarasite in lliis scalc ;ii-c llie 

 foUowing-' : 



I. The aliilily to grow in llie living cells of llic host. or, al leasl, nol killing 

 them unlil the life cycle is eonipleted. Tliis is perhaps the most signitieant 

 quality of the séries, since it may imply an adaptation ol' llie host as well as of 

 the parasite. 



'i. The ability to stimulale llie host to alinoriiial de\'elopiiieiiL. 



Ti. S|ieciali7.ation of parasilism ; (rr), thrn limilalion to a single host spe- 

 cies; [h], thrii allernation of hosts. 



4. The aliililx hi gniw in lin- lissnes of an (ithcrwisc licallhy host and lo 

 grow bélier the nioi-e xigonrons lin- hosl. 



5. Perl'ection ol' nieaiis of dispersai, the adaplalioii ol' spore prodinlion and 

 dissémination to llie parasilic existence, 



I. l,M"v 1,. . l;niisilisiiir ri \li,h„ihs,i„' ,l,ms la y,il„rr. \':\v\-. illOli. 



'2. i:r. Srirl~ C.-W. , fnwndniils „/ Ihr l:lllii,iii<ln, j'irai Sorirl,/ ,./ \] as/,ilu/loil. Mil. T.. |.p. I-T. 

 IS'.li;. 



-. Smiiii rii,-(,l.iil,l . Srinirr. S. S., \\, p. SI7, l'.HIi. 



