528 tETCH : 



The Microconidia. 



The microconidiophores arise as stout, lateral branches 

 practically perpendicular to the vegetative hypliae. The 

 branch usually springs from a narrow base, and almost 

 immediately swells out to a diameter greater than that of the 

 parent hypha. It grows on for from 30 to 100 (jl, increasing 

 slightly in diameter upwards until it attains 7 or 12 ji, ; for the 

 remainder of its growth it tapers uniformly, until it reaches a 

 length of from 90 to over 300 \k and an apical diameter of 4-6 {jl. 

 The conidiophore is cut off from the main hypha by a septum 

 shortly above the point of origin. If it is a short conidiophore 

 (about 90 a long), this is the only septum in it. But the 

 longer conidiophores have usually two or three additional cross 

 septa, the highest being about 80 a from the base, a little 

 below the point at which the conidiophore begins to taper. 

 The normal conidiophore, therefore, consists of a sterile basal 

 portion, which is one to three septate, surmounted by a long 

 tapering tube. All the septa are formed before the spores are 

 produced. The sterile base is often curved, but the long tapering 

 upper cell is always straight. The growth of the conidio- 

 phores is fairly raj)id. In one case an extension of 20 [j. occurred 

 in 23 minutes ; in another instance 70 jx in 105 minutes. 



It is not easy to observe the development of tlie microconidia 

 in hanging drops owing to the length of the microconidio- 

 phore, though occasional^ one may lie parallel to the cover 

 glass. The majority, however, j)roject from the drop into the 

 cell below. I have obtained better results by sowing the 

 spores in drops of a sugar solution placed on sterihzed slides 

 and covered by a large (1 inch square) cover glass supported 

 on four wax feet. By pressing down the cover glass, a film 

 of liquid of any desired thickness can be obtained, and 

 the conidio]>hores must develop horizontally, or nearly so. 

 Development, probably tln-ough lack of oxygen, is retarded 

 by this method ; but this is an advantage since it delays the 

 a})peaiance of the conidiopliores until the next day. When 

 the cultures are examined, the liquid may be prevented from 

 evaporating by placing strips of moist blotting paper round 

 the cover glass. Cultures made in this way remain pure 

 for four or five days, being kept, of course, between the 



