330 



couceutric circles of imiforni breadth about the point of infection. Fhially 

 the fi'uit is innnunifled, and according to Daiideno ('0(>)' there seems to 

 be a distinct produftion of cellulose in the cell-wall of the apple, and also 

 .'1 prodn<-ti(>n of stardi in the invaded cells. The walls become thick and 

 the fi'uit is temixiraril^' in a state of preservation. 



ETIOLOGY 



Tile disease is caused hy a fungous para.site, Spha-eropsis malurunu 

 Its general nature is that of a wound parasite, tliougli it fi'equently fol- 

 lows bliglit, thus acting as a saprophyte. Its pathogenicity has been es- 

 tablislied by Paddock ('00)- and by 8cott and Rorer (1. c, p. 49). The 

 writer has confirmed the work of these men, but at present the results 

 are not entirely satisfactory. In few cases has the canl^er been produced 

 by artificial inoculation even under tlie most favorable conditions. Tlie 

 only explanations at liand are that the fungus is strictly saprophytic or 

 that tlie work was not done at the riglit season of the year. Where maxi- 

 nuun sterile conditions were maintained and where tlie inoculations werf 

 made in early summer the writer has failed to reproduce the canker dis- 

 ease. Further experiments may show, how'ever, that infection is possible 

 if done at earlier seasons, perliai)s at the time of the ri.se of sap. Leaves 

 have been inoculated in all coiiceival)le manner, but only where spores 

 were sprayed on the under side were we able to produce "frog eye." i n 

 these cases al)uiidant fruit bodies appeared. Extended discussion, as re- 

 gards the p.'ithogenicily of the organism cannot be taken up hcrr. hut it 

 may be said that the present state of our knowledge is very unsatisfactory 

 and many exi)erinients will be ne('ess;iry to clear up these ix^ints. 



Hi/iKiiioni!/. — In literature we tiiid tlie fungus referred to as Sphacr- 

 op.si.s malornDi IJerk. and »S'. iniiloruiii I'k. Other names have been apiilied 

 to llie same s])ecies, so that it is only l)y making a careful outline of the 

 work (Idue. ti'aciiig it (lom its discovi-ry to tlie ]»resent lime, that the sit- 

 uation may become clear. 



r.ei'keley (';i(i)'' found .-i ruiigus wliicli he called Siiliinriii niiilonnii. 

 He described it as follows: "(dobusc en- subgloliosc, covered with a black- 

 ened cuticle; stroma blackisli. cuticle erumpent, more (tr less strongly 



''06. Danduno, J. H. A Stiiuuhm lo ih,- I'ldiluctiim of (VIJiiNw mikI Sliircli. Ui-pt- Midi. 

 Acad. Sci. 8:40-44. inoo. 



>'00. Paddock, VV. The Now York Apple Tivc ("anker (Socond Kt-port) X. V. aii'iieva) Arp. 

 Exp..Sla. Bui. 18.'>:205-2i;<. 1900. 



»'30. lierkidey, M.J. English Flora 5:257. l«3fi. 



