84 



Mycologia 



The present idea regarding the omnivorous nature of perono- 

 sporaceous fungi will have to be greatly altered, as is proved in 

 this case by inoculation experiments v^hich show an entire lack of 

 relationship among species occurring on closely related host plants, 

 even growing in the same field. Sawada also succeeded in making 

 the following three independent species from what has been 

 known as the lettuce downy mildew fungus, Bremia Lactucae, 

 which attacks 66 species belonging to 24 genera so far as has been 

 described. 



(i) Bremia sonchi K. Sawada sp. nov. in Shokubutsugaku 

 Zasshi (Botan. Magaz.) Tokyo, 28^-°: 80-83. Text fig. 2. 

 Feb., 1914. (Japanese.) 



Foliicolous or caulicolous; spots small, polygonal, rarely cover 

 entire surface in lower leaves ; aerial hyphae usually scanty, arach- 

 noid when appearing on lower leaves ; intercellular hyphae hyaline, 

 continuous, finally granulate, 8-1 7 /x; haustoria spherical, occa- 

 sionally obovoid or subclavate, 11-24X7-13/^ conidiophores 

 caespitous from stomata, whole length 230-560 /x, upper half 3-6 

 times dichotomously branching, the dimension of main stem, and 

 branches of first to fourth orders respectively measuring 286 X 9, 

 74 X 8, 65 X 6, 52 X 4, 43 X 3-5 basal portion of main stem 

 somevvdiat swelling, each branch rather slender, curved, rarely i- 

 septate throughout the conidiophore, swellings of terminal 

 branches spherical, 2-6 sterigmate, sterigmata 4-7 X 2.5-3 

 terminated by single standing conidia ; conidia mostly globose, oc- 

 casionally obovoid, flat-papillate above, small-pedicellate below, 

 containing protoplasm highly reflecting light, 17-24 X 13-21 /x, 

 germinate in 2 hours; germ tubes 3.5-6/1, diam., varying in thick- 

 ness through the growth. 



On Sonchus oleraceus. 



Locality : Taiwan (Formosa). Common. 



Illustration : One woodcut figure showing conidiophore, hau- 

 storia and conidia. 



Inoculation result is only positive on above plant, negative on 

 Crepis japonica, Lactuca dehilis, Lactuca laciniata, Lactuca 

 scariola var. sativa (Lettuce), Arctium Lappa, Hemistepta cartha- 

 moides, Sonchus oleraceus, and Taraxacum platycarpum. 



Chief morphological difference from B. Lactucae lies in (i) 

 the situation of lowest branch of conidiophore nearly at the 



