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The Dissemination of Disease by Means of the Seed of 

 the Host Peant. 



By M. F. Baeeus. 



(Abstract from thesis presented in June, 1908, at Wabash Collegee, Craw- 

 fordsville, Indiana, for Eastman Biological Prize.) 



It has been known for a long time that diseases can be spread by 

 means of the seed of the host plant. As early as 1730 Jethro Tull recom- 

 mended a change of seed to avoid smut. Since then the list of such dis- 

 eases has steadily increased until now there is a large number of them. 



A knowledge of the method by which infection of the seed takes place 

 and of the subsequent growth of the parasite is of value, since it will re- 

 veal a vulnerable point of attack, if there be any, in seeking means of 

 controlling the disease. It is the purpose of this paper to indicate briefly 

 those diseases of cultivated plants which are disseminated by means of 

 the seed of the host plant and to point out the method by which the seed 

 becomes infected. 



These diseases can be divided into two classes, those which infest the 

 seed internally, i. e., the organism entering the maturing seed and existing 

 within in a dormant condition until the germination of the seed ; and those 

 which infest the seed externally, i. e. the organism or its spores becoming 

 attached to the surface of the seed and entering the host plant at the time 

 it germinates. The diseases belonging to the former class are the An- 

 thracnose of Beans, the Blight of Peas, the Loose Smut of Wheat and 

 Barley, and possibly a few of the Rusts. Under the latter class may be 

 included most of the Smuts, the Wilt of Flax, and probably some of the 

 Rusts and a few Bacterial diseases. 



Bean Antheacnose. 



Colletotrichum Undemuthianum (Br. & Cav.) on Phaseolus vulgaris. 



The fungus causing this disease survives the winter in the seed of 

 the host plant. If the affected pods are allowed to ripen on the vines, the 

 mycelium of the fungus penetrates further and further, eventually entering 

 the seeds, usually causing them to become spotted (Figs. 1 and 2). Here 



