STEM NEMATODE ON WILD HOSTS. 7 



occasionally found growing entirely by itself, isolated by several feet 

 from any others. Frequently such isolated plants were diseased as 

 badly as those found in close association in thick beds. In one spot 

 near Newport, Oreg., scattered diseased plants were found at the 

 lower edge of a thick growth of salal {Gaultheria shollon) on the 

 face of a perpendicular bluff. Similarly with Hypochaeris, a single 

 diseased plant was found growing in a small pocket of soil at the 

 edge of a jagged rock more than 4 feet distant from any other vege- 

 tation. 



Nothing is known as to the chief agencies for the distribution of 

 this disease among wild plants. Besides the gradual spread through 

 runners or stolons, which occurs with strawberries, animals, birds, 

 wind, water, etc., readily occur to the mind as possible agencies of 

 dissemination. But even with these and other means active in help- 

 ing to spread the pest, it seems entirely unlikely that it could have 

 reached its present distribution during the time that it has been 

 known to occur on the cultivated plants in the same region. In fact, 

 as previously mentioned, the evidence seems to point to the conclu- 

 sion that the pest has been present on the wild plants for many years 

 and that it is now passing, in some localities at least, from the wild 

 to cultivated strawberries. 



It is just as possible to conceive of the nematode as a native of 

 that region as to conceive of the many native plants as having 

 evolved there. It is equally plausible, however, to recognize the pos- 

 sibility of the pest having been introduced perhaps a hundred years 

 ago when ships sailed from northwestern ports laden with lumber 

 and other products and came back sometimes with dirt ballast from 

 European ports. 



The interesting fact must be recorded here that Hypochaeris 

 radicata is, according to Piper and Beattie (8), a weed that is not 

 native to that section. It is said to* have been introduced from 

 Europe. This fact naturally adds considerably to the interest of the 

 problem, particularly in connection with speculation as to the origin 

 of the disease and how it has become so widespread. 



INOCULATION EXPERIMENTS. 



Inoculations were made as a rule by the rough but effective 

 method of simply breaking up diseased plants containing living 

 nematode material — eggs, larvae, and adults — and stirring them into 

 the soil. Careful observations showed that this releases the organ- 

 isms into the soil, from which they enter immediately any host plant 

 they may be able to infest. 



Shortly after the occurrence of the disease on cultivated straw- 

 berries in the Northwest became known in 1919, diseased specimens 

 sent to Washington, D. C, were used to inoculate Fragaria vesca, 

 F. virginica, F. platypetatu, and F. chiloensis, all of which were 

 successfully infected. No significance was attached to this at the 

 time, however, except in possible relation to future studies on re- 

 sistance. It was not until two years later that F. chiloensis was 

 found naturally infested. 



Inoculations of red-clover seedlings were made at Corvallis, Oreg., 

 with the wild-strawberry material, and typical infections were se- 

 cured. In Plate I, D, are shown typical diseased clover seedlings 



