234 BULLETIN 94. 



species. Different species of fungi may under some conditions 

 produce nearly or quite identical phenomena in the progress and 

 culmination of the disease. Some species develop phenomena 

 allied to genuine cases of damping off, and the final result of 

 which is practically the same, the decay of the stem near the sur- 

 face 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 dis- 

 cussing the several species of fungi which have been found to con- 

 tribute a share in the production of the disease it will be conven- 

 ient 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 identi- 

 cal troubles. 



THE POTTING BED FUNGUS. 

 Artotrogus debaryanus 1 (Hesse). 



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

 of young seedlings. It is very 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 house. 2 



It is thus a very common and unwelcome bed-fellow and pot- 

 companion of many seedling plants which are more or less crowded 



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

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

 bilis Schrank, Denkschr. d. k. acad. d. wiss. z. Munschen, 1813, 14) by Nees 

 von Esenbeck Nova acta acad. Leop. XI, 2,515, which belong to another 

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

 (Montagne, Sylloge, 304, 1845) was the next name which was used for a 

 member of this group and must consequently take the place of Pythium 

 Pringsheim, Jahrb. wiss. Bot. II, 303, 1860. 



2 Humphrey, 8th Ann. Rept. Mass. St. Agr. Bxp. Station, 221, 1860. 



