218 AGRICULTURAL EXPERIMENT STATION. [Jtm. 



the end of the first day (fig. 9). They may continue to 

 grow for about two days, in which time the germ tube may 

 become several times as long as the greater diameter of the 

 spore. If no nourishment be ol^tainable, growth ceases and 

 death follows. If, however, nourishment be provided in the 

 form of an infusion of prunes, for instance, the development 

 of the germ thread is very rapid, and the entire culture drop 

 is filled by a mat of strong and branching threads. The 

 difierence in development duo to absence or presence of 

 nourishment may be seen l)y comparing figs. 9 and 10, 

 which represent spores after one day's development under 

 these opposite conditions, respectively. Vigorous branches 

 of the mycelium grow upward into the air and downward 

 into contact with the glass sli[) supporting the culture. 

 No traces of spore formation could ever be detected on 

 the aerial threads, although carefully sought for. On the 

 branches which come in contact with the glass are produced 

 in all nourished cultures, and very aljundantly, certain 

 structures characteristic of this and related species of fungi, 

 and known as attachment organs. These organs a})pear to 

 be formed whenever branches of a growing mycelium come 

 in contact with firm unyielding ol)jects. They are produced 

 by the rapid and more or less exactly dichotomous branch- 

 ing of a thread, which, at the same time, becomes much 

 stouter and richer in protoplasmic contents than before. 

 The short and densely aggregated branches form a thick 

 tassel, which becomes attached by the free ends of its 

 branches to the substratum (fig. 11). At this time these 

 organs are readily recognized by the naked eye as small 

 darker spots on the glass of the culture sli]) or vessel. A 

 day after its complete development one of these organs 

 shows sio'ns of degeneration. Its dense contents begin to 

 l)econie watery and to disappear, and by the second day 

 there is left little but the empty outer walls, enclosing a 

 nearly or quite continuous cavity (fig. 12). The possible 

 or probal)le significance of these peculiar structures may be 

 discussed later. Slide cultures of spores in jn-une infusion 

 or similar thud medium rarely yielded anything besides 

 mycelium and attachment organs; but occasionally a small 

 yclerotium is developed, The vegetative development on 



