DEFINITION OF THK PARASITISM OF Fl'Niil. 3 



of boring through cell-walls, if the part be impregnated with a 

 stimulating solution. They behave la-re completely as parasites. 

 For example, hyphae of P>:ni<:ill /'///// glaucum penetrate into living 

 cells of a leaf injected with a two per cent, solution of cane 

 siiLiar, while without previous injection of the leaf they have 

 never been observed to do so. Penicillium is also known, in 

 certain circumstances, to beconif parasitic. 



Many species of fungi are capable of passing the whole or a 

 part of their life us parasites on living plants, (.Ymspieuous in 

 this respect are the Uredineae and I'stilagineae, many Ascomv- 

 cetes, including all Exoasceae and Erysipheae ; and amongst tin- 

 lower fungi, most of the Chytridiaceae and all the Peronosporeae. 

 Xor does this exhaust the list, for amongst the remaining t'lin-i 

 we may find isolated families, genera, and even species occurring 

 as parasites, while forms closely ivl,-itfd to them are saprophytic. 



To classify the parasites, saprophytes, and intermediate forms, 

 we shall adopt that arrangement proposed by Van Tieghem and 

 De liary. 



2. CLASSIFICATION OF I'ARASlTKs A N 1 > >A I'ROPH YTF.s. 



1. True saprophytes are such as regularly pass through their 

 whole life-history in a saprophytie manner. They may derive 

 their nourishment from different kinds of pabulum, or be limited 

 to some definite substratum. The true saprophytes do not come 

 within the scope of this book. 1 



2. Henri-saprophytes (the -facultative parasites' <>f l>e P.ary) 

 are wont to pass through their whole ili-velopment as saprophyte-. 

 but on occasion are capable of existing wholly or partially as 

 parasites. Anion-M them are included particularly such species 



may lie designated "occasional parasites," which commonly 

 occur as .saprophytes, and only under certain conditions become 



parasitic. 



3. True parasites (the 'obligate parasites' of he Bary). These 



undergo no part of their development as saprophytes, but live in 



every si age of existence as parasites. 



4. Hemi-parasites ithe 'facultative saprophytes' of he liary) 



are capable, if need be, of becoming -a|>ro]>h\ tes for a Season 



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Phanerogaou win. h li\.- i-\,-li^i\ fi\ - i|in.|iiiyii'- mi organic ilrl.i-i-,, in .-,,1,1 



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