856 EXPERIMENT STATION RECORD. 



and for 2 hours in a 1 per cent solution of cak-imn chlorid. The 

 results of the germination tests of the treated seed are shown, com- 

 parisons being made with seed soaked hours in water. AVith the 

 exception of the s(>ed treated with lysol, the germination of the other 

 lots of treated seed exceeded the check, while the number of diseased 

 plants w^as less. 



A second series of tests is reported, in which the effect of treatment 

 on diseases is shown. Normal seed gave 23.3 per cent of diseased 

 plants, and treated seed gave the following percentages of diseased 

 plants: Soaked in concentrated sulphuric acid, as above, 12.5 per cent; 

 seed removed from seed ball and treated with sulphuric acid, l-i.3 per 

 cent; soaked 2-1: hours in Bordeaux mixture, 20 per cent; shelled and 

 soaked in Bordeaux mixture, 16.6 per cent; soaked for 24 hours in a 

 copper sulphate-soda mixture, 12 per cent; shelled and soaked in a 

 copper-soda mixture, 9.2 per cent; shelled seed untreated, 10.7 per 

 cent diseased. 



As a result of his investigations, the author recommends as the best 

 and surest method of treatment the soaking of the seed in sulphuric 

 acid, as described above. The efficiency of the treatments with calcium 

 chlorid, copper-soda mixture, and carbolic acid is in the order named. 

 The last named should not exceed a i per cent solution. The experi- 

 ments in shelling seed showed that the advantage derived from the 

 treatment does not compensate the additional cost. 



The rotting of greenhouse lettuce, G. E. Stone and R. E. Smith 

 [Massachusetts Hatch Sta. Bul.GO.j^P- M\ P^>^- ^,»- 9,dgms. 7).— 

 The forcing of lettuce, which has become a very important industry in 

 Massachusetts, is liable to great loss on account of a number of para- 

 sitic diseases to which the plants are subject. The authors have been 

 carr3nng on the investigations for 5 years relative to a cause of these 

 diseases and means for their prevention. Their experiments have at 

 last been brought to such a point of completeness as to w^arrant pul)- 

 lishing the results in detail. The technical portions of their investi- 

 gations have been already published (E. S. R., 12, p. 761). 



As the result of their studies it was found that great confusion has 

 existed as to the cause of a number of diseases of lettuce. The fungus 

 most generally described as causing lettuce diseases is Botrytis md- 

 garis. This fungus is said to occur rather rarely as a parasite on well- 

 grown lettuce. It is commonly associated with the diseases indelinitely 

 known as " damping off'," mildew, black root, and rot. The most 

 serious disease of forced lettuce is that called " drop." This disease 

 has been found to be caused by the fungus jScIeroti/ualibcrtiana^vfhich. 

 has not previously been described as occurring on lettuce, but is known 

 to cause similar diseases on a ninnber of other plants. It is a fungus 

 that spreads through the soil and does not yield to the ordinary methods 

 of prevention. It is an active parasite, attacking and killing every 



