304 Agricultural Experiment Station, Ithaca, N. Y. 



culmination of tlie disease. Some species develop phenomena allied 

 to genuine cases of damping off, and the iinal result of which is 

 j^ractically the same, the decay of the stem near the surface of the 

 ground and the collapse of the seedling. 



Some variations in the external appearance furnish diagnostic 

 characters correlated with the presence of certain species of the 

 parasite, but it is doubtful if in any case the specific cause should 

 be confidently asserted without recourse to microscopic examina- 

 tion, sometimes to be preceded by special treatment. In discussing 

 the several species of fungi which have been found to contribute a 

 share in the production of the disease it will be convenient to take 

 up first the species to which the trouble is generally attributed, and 

 then to follow with others which play a more or less important part 

 in the development of similar or nearly identical troubles. 



The Potting Bed Fungus. 

 ArtotrogiLS debaryanus ^ (Hesse). 



This fungus is responsible for a large part of the damping oif 

 of young seedlings. It is veiw widely distributed, being very com- 

 mon in the soil of gardens and also in the forcing house. It is 

 common also in many fields, but it probably is more abundant in 

 soil where numbers of plants are grown from the seed in a more 

 or less crowded condition, especially those plants which are known 

 to be predisposed to its attacks. It has, however, been found in 

 virgin soil taken freshly from the woods into the forcing ho use.^ 



It is thus a very common and unwelcome bedfellow and pot- 

 companion of many seedling plants which are more or less crowded 

 in the seed bed or forcing pots of our gardens and hot houses, 

 especially if undue moisture is present in the soil. In the gardens 

 it is frequently impossible to control the amount of moisture in the 

 soil, and in the forcing house where often the light is defective, the 

 air is not fresh or it is supercharged wdth moisture, it is often nearly 



1 Pythium debaryanum Hesse. The name Pythium was used in 1823 as a 

 generic name for two species (Mucor spinosus Schrank, and M. imperceptibilis 

 Schrank, DenkscLr. d. k. acad. d. wiss. z. Munscbeu, 1813, 14) by Nees vou 

 Esenbeck Nova acta acad. Leop. XI, 2,515, wbich belong to another geuus 

 (Achlya, see Fischer, Rabenhorst's Krypt. Flora. IV, .332). Artotrogus (Mon- 

 tague, Sylloge, 304, 1845) was the next name which was used for a member of 

 this group aud must consequently take the place of Pythium Priogsheim, Jahrb. 

 wiss. Bot. II, 303, 1860. 



2 Humphrey, 8th Ann. Kept. Mass. St. Agr. Exp. Station, 2>1, 1860. 



