The Fungus Pests of Garden Plants 



damp soil the spores remain in a resting condition until they are 

 afforded an opportunity of multiplying with the marvellous rapidity 

 that invests the disease with its terrible power. A series of six 

 illustrations, five of which are highly magnified, will enable the reader 

 .to follow the development of Phytophthora infesta?is. 1 



The illustration No. i shows a Potato leaf on a reduced scale dis- 

 figured by the attack of the fungus. The Phytophthora is sending 

 mycelial threads (called hyphae) in all directions through the substance 

 of the leaf, feeding on the protoplasm of the cells and destroying the 

 chlorophyll, or leaf green, in those cells. 



No. 2 shows the fungal threads at 

 work. In a diseased Potato plant these 

 threads, or mycelial hyphae, make their 

 JB way through the substance of the leaves, 

 and down the haulm into the tubers, 

 SE from which they consume the food stored 

 there. 



No. 2 



No. 3 



No. 3 exhibits the various stages of germination of one of the 

 conidia of Phytophthora infestans : (a) the ripe conidium in water ; 

 (b) protoplasmic contents breaking up into blocks, which separate 

 and escape (c and d) as minute kidney-shaped zoospores (e) each 

 with two cilia ; (/ and g) the zoospore coming to rest and losing 

 its cilia ; (h, /, /, and K) successive stages of germination of the 

 zoospore. 



No. 4 represents a longitudinal section of Potato-stalk with 



1 For permission to reproduce the engravings numbered i, 3, 4, and 5 from 

 Professor Marshall Ward's Diseases of Plants,' we gladly acknowledge our 

 indebtedness to the Society for Promoting Christian Knowledge. Professor W. 

 Carruthers has kindly allowed us to use the illustrations numbered 2 and 6. 



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