spore-formation of Acrospeira mirabilis. 137 



If the chlamydospores were sown on a watery extract of chest- 

 nuts made up with agar-agar a further crop of chlamydospores was 

 produced and at the same time the submerged hyphae formed 

 small bunches of flask-shaped structures from which endoconidia 

 arose. The more dilute the chestnut extract the greater was the 

 abundance of these endoconidia, so that on germinating the 

 chlamydospores in water or in agar-agar practically a pure culture 

 of them could be obtained. 



When the chlamydospores were germinated in beer-wort gela- 

 tine however no sign of these endoconidia could be found on the 

 submerged hyphae but they became shortly septated into barrel- 

 like cells, some of which grew rapidly into large ellipsoidal 

 structures in which the protoplasm became finely vacuolated 

 while the walls thickened and became carbonized. On placing 

 these structures in water they cracked in the course of a few days 

 and let free swarms of minute, slightly motile, spherical bodies. 

 Presumably these structures were sporangia but so far all attempts 

 to germinate the " spores " have failed. At the same time the 

 aerial portions of the mycelium again formed the characteristic 

 chlamydospores. Sowings on gelatine or agar-agar made up with 

 Klebs' solution and 5 °/ cane sugar or glucose gave rise to pure 

 cultures of these " sporangia." 



In cultures on chestnut-agar five weeks or more old or in the 

 cotton-wool plugs, used to keep the chestnut cultures moist, a 

 further spore-form has been produced which consists of a group of 

 chlamydospores surrounded by a thick envelope of several layers 

 of cells. They arise from the same coils as the chlamydospores 

 already described when little nutriment is available. 



These spore-balls have been germinated on the media pre- 

 viously used with the following results : on pea-extract the 

 mycelium was sterile, on chestnut-agar endoconidia were produced 

 but not so abundantly, and on beer-wort gelatine "sporangia." 

 On the two first media numbers of cell- fusions occurred especially 

 when the food supply was limited. At the same time on the 

 chestnut-agar large crops of spore-balls were produced but they 

 differed from those formed on the old chestnut cultures in having 

 only a single layer of envelope cells — like a typical Urocystis. I 

 have since found this same form in diseased chestnuts, so it must 

 be assumed to be the normal one. The development of the 

 abnormal form will be considered later. 



The cultures on beer- wort gelatine besides forming "sporangia" 

 gave rise to arches or spirals of cells which became strongly 

 swollen and carbonized. They resembled the ascogonia described 

 by Tulasne and others in Ascobolus 1 and were externally very 



1 Tulasne, Anns. Sci. Nat. 5me Ser. vi. p. 215, Janczewski, Bot. Zeit., 1871, 

 p. 257. 



