The Scottish Naturalist. 



121 



I made my investigation on the Phytopdus that causes the well- 

 known bud-deformity on Corylus (Hazel), and placed distorted 

 buds of Corylus, which I had previously cut open, on Brassica 

 nigra, Sisymbrium austriacum, Capsella Bursa-pastoris and Mya- 

 grum perfoliatum. In Sisymbrium, Capsella and Myagrum I 

 obtained bracts to the flowers, and in Myagrum, in addition, there 

 were slightly doubled flowers. 



Bellis perennis (Daisy), which I infected with the Phytoptus from 

 Valeriana tripteris, Corylus, and Campanula Tenorii, behaved 

 essentially in the same manner with all these different parasites. 

 The rosette-leaves were abnormally hairy, but without forming 

 an erineum, some flowers of the disc were green (virescent), and 

 the phyllaries of the involucre were somewhat lengthened. 



As an often repeated phenomenon I observed that after success- 

 ful infection, the growth in length of the branch became slow, and 

 that even where abnormally-formed organs did not occur, the 

 formation of axillary buds was promoted. Thus in several species 

 lateral shoots were formed, e.g. in the inflorescence of Euphorbia 

 Peplus after infection with Phytoptus Coryli, and also in Capsella 

 Bursa-pastoris. Crowding of the buds was also characteristically 

 present. 



The choice of plants on which the experiments were undertaken 

 was quite accidental. The inducement to select them was only 

 that I found examples of Valeriana tripteris in the wild state with 

 doubled flowers, in the deformed flower-buds of which I found 

 Phytoptus. It would be extraordinary if only in the Valerianacece, 

 Cruciferce, and Linaria Cymbalaria reactions should follow infection 

 with the parasites in question ; hence it is extremely probable 

 that a procedure has been obtained by which one can bring about 

 artificially abnormal deviations in structure in a very large number 

 of the most varied plants besides the Valerianacece. 



The investigations show clearly that by the reciprocal influences 

 of organisms on one another new diseases originate ; and they 

 call attention to a previously little regarded side of symbiosis ; and 

 they give an additional support to the teaching that by far the 

 greater number of diseases and abnormalities in structure are 

 brought about by parasitic organisms. 



