288 Pflanzenkrankheiten. 



Peltier, G. L., A consideration of the physiology and life 

 history of a parasitic Botrytis on Pepper and Lettuce. 

 (Missouri bot. Garden. 23. Ann. Rept. p. 41—74. PI. 1—5. 1912.) 



The writer gives the foUowing discussion and conclusions. 



There can be no question but that the disease on the peppers, 

 lettuce and other plants in the greenhouses of the Missouri Botanical 

 Garden was caused by Botrytis cinerea, which possessed the power 

 of penetrating the plant tissues and destroying them. 



The lettuce „drop" due to Botrytis cinerea has about the same 

 charasteristic Symptoms as when caused by Sclerotinia Libertiana. 

 It is, indeed, interesting to note the similarity between the Symptoms 

 of the disease described by Stevens and those noted by the writer. 

 Even the physiology of the two fungi agree to a large extent. The 

 diflference is that Botrytis produces only conidia, whereas 5. Liber- 

 tiana only ascospores. In this connection it is interesting that the 

 author has been able to develop from Botrytis a mycelium that 

 does not produce conidia. From the writer's observations it appears 

 that the more parasitic the Botrytis becomes, the greater is the 

 number of sclerotia and the fewer the conidia produced. 



That Botrytis can become a serious disease was very well shown 

 in the greenhouses. To become parasitic it must have suitable con- 

 ditions. The life cycle of the fungus is complete with the germina- 

 tion of the sclerotia, resulting in the production of conidiophores. 

 This appears to be the prevailing type of Sclerotium germination. 

 Istvanffi is the only one who in recent years has been able to 

 obtain ascospores from sclerotia of Botrytis. Since he was unable to 

 produce infection by means of the ascospores, he failed to complete 

 the life cycle of the fungus. Apothecia were rare; the sclerotia 

 formed conidiophores more commonly. It may be safely stated, then, 

 that the Botrytis causing lettuce "drop" and similar diseases is a 

 degenerate form which has lost the apothecial stage. The Botrytis 

 cinerea causing this disease and that of peppers and other green- 

 house plants, at the Missouri Botanical Garden, is the imperfect 

 stage oi Sclerotinia Fiickeliana De Bary. It is a degenerate form, having 

 lost the apothecial stage entirely, the life cycle being completed 

 when the sclerotia germinate by the production of tufts of coni- 

 diophores. 



In all cases Sclerotinia Fuckeliana has no connection whatsoever 

 with vS. Libertiana Fuckel. 



Work on the parasitism of Botrytis is still in its enfancy and 

 many further experiments will be necessary before the interrelations 

 with its host are fuUy understood. The author's results show that 

 there are two stages in the disintegration of the plant tissues. There 

 can be no question that some substance is secreted by the fungus 

 which kills the plant cells in advance of the mycelium. The author 

 disagrees with Smith that the poisoning effect is due to oxalic 

 acid, since delicate tests for this acid gave only negative results. 

 Even in old sugar cultures on which the fungus has been growing 

 for several weeks, no oxalic acid was present. Smith reports that 

 he found as high as two per cent of the acid under like conditions. 



The harmful substance may be some organic acid other than 

 oxalic, or it may be a toxic of some kind, which, however, is not 

 destroyed by heating to 100° C. The writer has found that weak 

 concentrations of malic, tartaric, oxalic, gallic, and acetic acids have 

 an action on the lettuce tissues similar to that of the mycelialextract. 



From the cultural work the author has found that a number of 



