EFFKi.TS OF PARASITIC Fr.Ni.I o\ Tlssi Ks OF BOST. 41 



e nails of this kind are cells of Pilulmln* A'/.///// inhabited 

 by ]'linti-<t<-Ii,-lus fulf/ciis, cells of turnip infested by /V//.S//M.///... 

 jjlmra, or of dandelion with X// //<// //////////. 



Cell-enlargement resulting from the influence of extracellular 

 parasites is most distinctly seen in those algal cells, which 

 form lichens with the hyphae of certain fun-i. Thus according 

 to Staid, tlie algal cells of the lichen /,'/;>/<</,//,/ y///.s/7/////< 

 become enlarged six-fold. 



Cell-enlargement accompanies all hypertrophy of plant organs, 

 whether the parasite lives purely intercellular, or has haustoria. 

 At the same time one generally finds a di.-appearance <>f the 

 intercellular spaces present in the normal tissues; in some 

 special cases, however, these may become more numerou- and 

 larger. Cell-enlargement, accompanied by disappearance of 

 normal intercellular spaces and chlorophyll, are shown by 

 Woronin's illustrations to be very marked in the -alls on cow- 

 berry, due to E.i-i,l)tixi<ltiini vaccinii. ('ell-enlargement is also 

 frequent in cases of hypertrophy due to Exoasceae : thus in 

 rj>/n-i'ii'i aurea, although the mycelium is only subcuticular 

 or penetrates but slightly int<> the epidermal layer, yet the 

 ells are much enlarged and their walls are strikingly thickened 

 ( Kiu. '>"). Smith 1 found that when leaves became thickened 

 in consequence of attacks of certain species of Y'/<// //'/>", their 

 cells became larger and rounder, so that the large intercellular 

 spaces of the spongy parenchyma disappeared and the char- 

 acteristic appearance of that ti-sue was lost. 



The epidermis, as has already been indicated, is intliience.l 

 ; '\ fungi which live between the cuticle and cell-wall, a- \\ell 

 as by epiphytic fungi, whose haustoria penetrate it. The 

 epidermis is, however, more frequently destroyed by endoph\ 

 vvliicli rupture it in forming their reproductive or-ans. Some 

 of these produce their sporocarps inside the epidermal cells, 

 and, as they eidaru 1 ', CRU86 ilctaclimciit of the outer walN of 

 the cells from the remainder, to form for a time a covering 

 which is ultimately ruptured as the sporocarps attain maturity. 

 When- the t'un-i live under the cuticle (e.g. the ExoaSd 

 this alone is ruptured when the asci arc formed. The iepro- 



William <. Smith. I'litrisn. -1111111: '1. Mm |ili"l"ji'- it. Ainti'inh- il. ilni-i-li 

 K\'p.i-'-i-i-!i \i-iui-.n-lili-n I )i-|ni mat ilium. " liiiiilL.'. I >i-~'-l t.it inn, Milhl.li. ]s''l; 



i, /'"/<//</< -niitit,-ii-;*i. Zeittchrift. Is'.U. 



