184 PHYTOPHTHORA PARASITICA. 



growing point and thereby kills the seedling. If the seedling is kept 

 in a very moist atmosphere the inoculated stem produces in forty- 

 eight hours a white fluffy aerial mycelial growth, bearing sporangia. 

 The hyphse project about a millimetre or two from the stem. But 

 stems of plants out of the seedling stage seem to be immune from 

 the attack and artificial inoculations have proved unsuccessful on 

 these. When the ordinary method of inoculating, by means of 

 putting a drop of water containing freshly discharged zoospores on 

 these stems failed, Klebahn's 1 method, employed by him in inoculat- 

 ing leaf buds of lilac plants, was tried. The stems of young plants 

 about three to six months old were surrounded by a jacket of dis- 

 tilled water, containing motile zoospores, in a glass tube about four 

 inches long and three-fourths of an inch broad, the lower end of which 

 was plugged by a rubber cork cut into two equal halves and having 

 a central bore just big enough to enable the two halves to surround 

 the stem without injuring it. This end was made water-tight by 

 means of moulding wax (Plasticine) or paraffin ; the upper end was 

 kept open. A young seedling was inoculated in the same way. 

 The result was that the stem and the base of the petioles of the 

 seedling in two days distinctly showed marks of successful inocula- 

 tion and in four days it wilted. The photo (Plate X), taken on the 

 fourth day after inoculation, shows the progress of the attack from 

 the petiole to the leaves. The plants three to six months old 

 remained quite healthy. Only one plant out of half a dozen such 

 inoculations on plants with matured bark, showed a small blackish 

 patch about a couple of centimetres in length, in two days after 

 inoculation. As the diseased area was found not to grow further, 

 even after a week, sections were made at this place. A few 

 hyphse were found confined to the epidermal cells only. They 

 were unable to grow further into the stem and the consequent 

 lack of food killed them. The inoculation failed even when the 

 stem was wounded. The reason of the parasite not attacking 

 stems of plants as soon as they are out of the seedling stage is 



1 Klebalin, H. loc. cit., p. 55. 



