REPORT OF THE SOCIETY 95 



have been studied more particularly: Asclepias syriaca, Convolvulus septum., 

 Norus alba, Lactuca canadensis, Apocynum sp., Ldctuca saliva Hieracium 

 auraniiacum. Taraxacum officinale Ficus sp. Sonchus spp., Euphorbia sp. Che- 

 lidonium majus. Evidences of the presence of protozoa have been found in 

 certain other plants but no detailed study has yet been made of these. No des- 

 cription of these organisms will be given in this preliminary note, as the writer 

 is engaged in the preparation of a series of longer papers on the subject. 



In addition to its intrinsic interest to the protozoologist, the study of this 

 subject may possibly throw new and important light on certain phases of applied 

 pathology. In the first place many plant pathologists are convinced that pro- 

 tozoon-like organisms may be concerned in the etiology of certain obscure 

 diseases of plants. In the secdnd place, there is a close parallel between the 

 relations of these organisms, which are probably primarily insect parasites, to 

 their plant hosts, and the relation of similar insect parasites to their secondary 

 vertebrate hosts. It has already been suggested that plants may serve as the 

 reservoirs of certain human diseases. Franchini has shown that several patho- 

 genic human protozoa will live and grow in latex. He has also succeeded in 

 inducing infection in white rats by inoculating them with protozoa derived 

 from the latex of plants. At the Cincinnatti meeting of the American Associa- 

 tion last December, Dr Richard Strong announced that one of these plant 

 parasites, having passed through the body of an insect and a reptile, is capable 

 of parasitizing mammals. 



Leptomonas davidi is associated with a definite gummosis of Euphorbia. 

 In none of the plants which I have studied have I be enable to detect any 

 disease S3^mptoms indubitably associated with the presence of protozoa. In 

 most cases the plants are outwardly healthy, and where parasitized plants show 

 disease symptoms a connection between these symptoms and the presence of 

 protozoa has not been established since plants of the same species are found 

 heavily parasitized without showing any lesions. 



The organisms apparently pass the winter as minute resting cells, in the 

 stems of shrubs or in the overwintering roots of herbaceous perennials. In 

 two flats of Hieracium grown in the greenhouse during the winter, the organism 

 remained in the resting stage in the latex in all parts of the plants. The plants 

 were very robust and healthy but there was no appreciable growth until the 

 approach of spring. With the commencement of growth in the plants the para- 

 sites also began to elongate and assume the active condition. Tropical plants 

 growing, in the greenhouse contained active protozoa in their latex throughout 

 the winter. There is evidently then a rhythmic adaptation between the endo- 

 phytic protozoa and their hosts. 



In two cases, Asclepias syriaca and Convolvulus sepium., the writer has disco- 

 vered that the organisms, a flagellate and an amoeba respectively, may pass into 

 the seed in the resting stage and later infect the seedling. This, together with 

 the adaptation mentioned in the preceding paragraph and the apparent absence 



