OBSEEVATIONS ON THE GENUS PYTHTUM. 489 



In any vigorous cultivation they become formed at an early 

 stage, and are scattered around in large numbers as develop- 

 ment proceeds. 



Besides these terminal conidia, however, there usually 

 appear numbers of interstitial conidia (fig. 4), each of which 

 arises as a simple swelling on the course of a hypha, which 

 having received much granular protoplasm, becomes at length 

 cut oiF by a septum on either side. In fig. 4 are shown the 

 various changes of the slowly moving vacuoles, &c., noticed 

 in such a body, observed for some time at intervals during 

 development. 



Each kind of conidium acts as a simple asexual reproduc- 

 tive cell. If fresh water containing oxygen be added to the 

 specimen, the conidia soon put forth processes which develop 

 forthwith into new extensions of the fungus ; this happens 

 whether the conidium be free or still attached (figs. 5 and 6). 

 If allowed to remain undisturbed, no germination occurs ; the 

 terminal conidia drop off and remain dormant, and the intersti- 

 tial ones become free by the decay of the remnants of hyphse on 

 either side. Under proper conditions their vitality is main- 

 tained for months,^ ready to be called forth in a few hours 

 when fresh water is added ; the older conidia usually show a 

 better developed " exospore " than those which have not been 

 kept. 



Germination consists simply in the extrusion of the '^endo- 

 spore " into a simple tube (from one or two points) into which 

 the protoplasmic contents pass, until all is used up in the for- 

 mation of the germinal tube ; the latter grows quickly by 

 apical growth, enters a suitable nidus by boring through the 

 cell-walls, or, if none such is present, soon decays. It is note- 

 worthy that the formation of septa originates when the repro- 

 ductive organs commence to be developed ; in its young stao-es, 

 the mycelium, though copiously branched, consists of a con- 

 tinuous series of tubes. 



> De Bary says that drought and frost are withstood by these conidia, 

 ' Bot. Zeit.,' 1881, No. 33, p. 524. 



