138 Mr Biff en, Note on some factors, etc. 



different from the Eurotium-Wk.e helices from which the spore- 

 balls developed. In spite of their carbonized walls these struc- 

 tures are not chlamydospores, at all events at present, and some 

 facts point to their further development along the lines of Ascobolus 

 or some such form. 



It is thus peculiarly interesting to note that one can not only 

 determine which form shall be produced by varying the food 

 supply but even intermediate forms can be raised by mixing the 

 two media. Moreover by transferring a culture producing these 

 " ascogonia " to a dung decoction, on which spore-balls are nor- 

 mally formed, the fungus makes the attempt, often it is true 

 unsuccessfully (for the cells of the ascogonia are sometimes 70 — 

 80 /u, in diameter), to enclose them and so produce the spore-ball 

 type. 



So far these results may, I think, be attributed merely to the 

 effect of the varying food supply. Within the last year or so 

 though Klebs has shown that altering the rate of transpiration is 

 a potent factor in determining the form of spore-development. It 

 may merely alter the external character of the spore or a totally 

 different spore-form may be produced. 



In Acrospeira I have only found cases in which the external 

 characters of the spores have been changed. Thus the chlamydo- 

 spores first described when grown under water instead of in the 

 air had thin, smooth, and uncarbonized walls instead of the thick, 

 brown, warted walls 1 . If however transpiration was abnormally 

 rapid, as for instance when the cultures were placed in a dry 

 incubator or removed from the tubes and left exposed to the air, 

 the chlamydospores had exceedingly thick, smooth, carbonized 

 walls, and were only about half the normal size. The case of the 

 spore-balls was still more interesting for the difference between 

 those produced on old chestnut cultures and on the chestnut-agar 

 plates was great enough to found separate species on. 



It was found that by keeping the cultures producing the 

 helices from which the spore-balls developed very moist that 

 instead of short balloon-like branches being put out from the 

 helix which at once became adpressed to it to form the single 

 envelope layer, long hyphae were formed which coiled together in 

 a snake-like fashion and ultimately gave rise to the many-layered 

 envelope. 



These branches themselves appeared to be potential sporo- 

 phores, for on liberally feeding them in the early stages of their 

 formation they too grew out into the characteristic helices. 



1 Cf. Klebs, Prings. Jahrb., 1900, p. 80, for similar experiments with Hypomyces. 



