THIELAVIOPSIS PARADOX A. 539 



were set free by the destruction of the upper part of the wall 

 of the parent cell — may have been only arrested macroconidia 

 as described above. 



A similar development occurred in flask cultures, to which 

 • 2 and • 3 per cent, of hydrochloric acid and • 09 and • 1 

 per cent, of sulphuric acid, respectively, had been added. The 

 mycelium developed in the form of rather compact submerged 

 spheres, which turned pale brown at their surfaces. These 

 spheres bore large numbers of suppressed macroconidia, but 

 no other spores. In general, the conidiophores were not curved, 

 and each bore one conidium only, but instances of two or three 

 in a chain within the conidiophore were found. 



Micro- V. Macro-conidia. 



Tlie separation of the two forms of conidia on the basis of 

 "size is to some extent misleading. I have measured micro- 

 conidia, 17 and 32 jx in length, though they rarely approach 

 the latter size. On the other hand, macroconidia, 8 X 5 jx or 

 d X 7 \)., are not uncommon ; and these are smaller than the 

 average microconidium (11-14 X 7-9 ^). Howard's method 

 of separating the two kinds of spores — by beating up the 

 mycelium in water and allowing it to subside, whereby he 

 supposed the upper layers contained chiefly microconidia — 

 must therefore be regarded as fallacious. Wlien the spores 

 are recently formed but have changed colour, it is possible to 

 identify the macroconidia by their more oval shape, their 

 more vacuolate contents, and by the fact that they are some- 

 times united in chains ; but many doubtful cases occur, and 

 all these criteria fail when the spores are old and blackish- 

 brown. 



Practically, the only constant difference lies in the mode of 

 formation of the spores and the structure of the conidiophores. 

 The microconidiophore is the longer, and terminates in a long 

 tapering tube, while the macroconidiophore is a short branch, 

 of almost uniform diameter when empty ; the former produces 

 a large number of spores, up to eighty or more, while the 

 latter produces twenty at most, and sometimes only one. The 

 microconidium acquires its wall within the tube, and hence is 

 cylindrical when extruded, but the wall of the macroconidium 



