A SNOWDROP DISEASE. 



43 



hanging drop of a decoction of dung produced in the course of five 

 days, in addition to a copious development of organs of attachment, 

 several tufted short conical branches, each branch bearing a chain of 

 globose colourless bodies at its apex resembling conidia in appearance ; but 

 these bodies will not germinate, and their function is problematical (8, fig. 4). 

 These peculiar bodies are described as follows by Woronin,* " kleinen, 

 spermatieniihnlichen, unkeimfahigen, perlenartigen Sporidien," who con- 

 siders them as very characteristic of the species of Sclerotinia. 



So far as my experience goes Botrytis conidia will not germinate in 

 tap-water containing one per cent, of cane sugar, and germination in tap- 

 water alone is very tardy and weak. 



A parasite called Botrytis parasitica, Cav., absolutely indistinguish- 

 able morphologically from the Botrytis attacking the Snowdrop, occurs as 

 a destructive parasite on Tulips, and the general account given above applies 

 in every detail to this Tulip parasite. Here, however, the resemblance 

 ends, and physiologically the two are quite distinct. 



When a mixture of Tulip and Snowdrop bulbs is planted in soil in a 

 glass vessel as described above, and ^^gorous mycelium produced by 

 conidia of the Snowdrop parasite is placed in the nutritive solution, the 

 Snowdrops are only attacked ; whereas when mycelium produced by conidia 

 from a diseased Tulip is introduced it only attacks the Tulip leaves. In 

 some instances the conidia for the above experiment were obtained 

 directly from diseased plants, in others the conidia came from sclerotia 

 that had formed in a nutrient solution and had been kept imtil the spring 

 folloA^ing their formation. 



Now if it is considered imperative that species should be founded on 

 morphological characters, as personally I think they should, it follows 

 that the parasites attacking Snowdrops and Tulips respectively constitute 

 one and the same species, and we must consider the two parasites as 

 physiologically differentiated forms of the same species. Further experi- 

 ments will probably demonstrate that such physiological races of a 

 common species of Botrytis are much more numerous than is at present 

 suspected. 



Wakker, who investigated a Hyacinth disease caused by a Botrytis,f 

 found on experimenting that onions could not be inoculated by the conidia 

 of the Hyacinth Botrytis. 



Saccardoi enumerates 140 species of Botrytis, characterised by measure- 

 ments of the conidia, and more especially by the host they grow upon ; but it 

 is very probable, at least in the subgenus Polyactis, to which most of the 

 destructive forms belong, that the majority will eventually be proved to 

 be nothing more than physiologically differentiated forms or races of 

 Botrytis cincrca, Pers. 



Those who have had experience know perfectly well that when a 

 Botrytis is grown artificially in different media, and under varied 

 conditions as to temperature, density of culture medium, kc, the general 

 habit, and size and form of the conidia vary to a much greater extent than 

 would be required for the establishment of a new species, judged from 

 the standpoint of specific characters as given by Saccardo. 



* Mem. cle VAcad. Sci. de St. P^tersb. viii. ser., vol. x., 1000, p. 22. 

 t ArcJiiv. Xi'i'rlandaises, xxiii. J Syll. Fung. iv. 



