2 FUNGOID DISEASES 



it will be seen that they form a number of classes 

 which have probably arisen by the degeneration (it 

 may be said through the loss of chlorophyll) of 

 forms in various groups of green, or at least chloro- 

 phyll-containing, low water-plants called algce. 

 Owing to their being devoid of chlorophyll, they 

 are entirely dependent for their food on matter al- 

 ready built up, either by higher plants, or by ani- 

 mals. Those deriving their nourishment from 

 living organic matter are called parasites, others 

 deriving it from dead matter are called saprophytes 

 (see p. 1 2). 



Before passing on to the actual plant diseases, a 

 few botanical terms must be described and a little 

 general information given in order to make the 

 context of the book more easily understood. 



HyphcB. — Most fungi have their vegetative part 

 (the body of the fungus, or that part which takes 

 up food) in the form of very fine delicate threads 

 called hyphae (Fig. i), which are mostly invis- 

 ible, singly, to the naked eye. They are in reality, 

 fine transparent tubes containing a semi-fiuid sub- 

 stance called protoplasm, which is the vital part. It 

 circulates slowly inside these tubes, and in it are em- 

 bedded numerous nuclei, fat globules, etc. Growth 

 of the hyphae takes place at the tip. 



Mycelium. — Usually the hyphae do not remain 

 long as single threads, but branch and re-branch, 

 becoming thereby interlaced and forming what is 



