Q, NATURAL HISTORY BULLETIN. 



no cell belonging to the host-plant, but merely a very much 

 swollen stalk-cell. This was demonstrated as described by 

 Sadebeck. bv a comparative investigation into the historical 

 development of the species and by the use of the reagents 

 and stains which produce different effects upon host and 

 parasite. Although the possibility remains that a mycelial 

 Exoascus exists which develops In the epidermal cells and 

 forms no sub-cuticular hvmenium. still the probability is great 

 that there is no AscoinyccS' in the sense of Magnus. 



For the comparative historv of development and biology of 

 the parasitic £.xoascccB I must simply accept the residts of 

 various authors. Mv work has been almost entirely upon 

 material collected when mature and preserved either in alco- 

 hol or dried for the herbarium. A most interesting research 

 could be made bv the use of artificial cultures and by arli- 

 ticiallv infected host-plants. This has been attempted, but I 

 have learned of no entirely satisfactory results. Brefeld. wha 

 has had the most experience in these lines, could keep the 

 germinating spores of £.xoasciis defor>iiaiis. for example, upon 

 culture media for months, but they refused to form mycelial 

 threads until transferred to young shoots of living plants. 

 Sadebeck with spores of Exoascii^ to<.quinetii (West.) Sadeb^ 

 was able to witness the entrance of mycelial threads through 

 stomata of the voung leaves of Aliuts: he also was successful 

 in inoculating .l/jit/s iucaua with the spores of Excxncus 

 epiphxUus. which he considers the easiest species to produce 

 disease in this manner. 



The results of inoculation not being entirely satisfactory, 

 Sadebeck worked out the history of development of the 

 majoritv of the species upon the naturally diseased hosts. 

 For the genus MagiiusicJIa he referred to the researches of 

 Rostrop. The biological historj- of Exoasciis pnmi has been 

 given bv de Barv ('8/ ). and that of Tafhriua aurca Fries, by 

 Magnus (75). 



It mav be of interest to indicate the limits and divisions of 

 all the Exoasccce as set forth b}- Professor Sadebeck. Bre- 

 feld had pointed out that the so-called •• Gynnwasn"'^ belong 



