538 t'ETCH : 



available. It is interesting to note that when the spores of 

 Thielaviopsis are sown in nutrient solutions which contain 

 poisons in a concentration approacliing that whicli inhibits 

 their germination, the Stysa7ius-\ike form is frequently pro- 

 duced; small floating islands of mycelium appear, and tliese, 

 after- bearing a few micro- and macro-conidia in the usual way, 

 produce the upright fructifications. 



The most puzzhng feature about these compound fructi- 

 fications is the fact that they are composed of microconidio- 

 phores. Under normal conditions the microconidiophores are 

 the first form produced by Thielaviopsis, and they are soon 

 succeeded by the macroconidiophores. But, in the Stysanus- 

 like fructification, there is a return to microconidiophores 

 when the conditions of growth are unfavourable. This would 

 appear to negative any supposition that the production of the 

 two kinds of conidioplxore is dependent upon the available 

 supply of food. 



Nothing has been observed which would tlu'ow any light 

 on the cause of the change from the production of inicro- 

 conidiophores to the production of macroconidiophores. The 

 macroconidiophore appears to be a depauperate form of the 

 microconidiophore, but the return to microconidiophores, when 

 the culture is old or when the conditions are unfavourable, 

 would seem to render inadequate any explanation based on 

 food supply or substances excreted by the fungus during its 

 growth. 



Variation in the Macroconidiophore. 



In old hanging-drop cultures, the macroconidiophore 

 frequently fails to open. The upper part of the conidiophore 

 usually becomes curved, either in simple hook fashion or in a 

 complete coil, and its contents round off into one large oval 

 spore mass or segment into a chain of two or three. These 

 spore masses then acquire a spore wall and turn black, while 

 still retained within the conidiophore. They are arrested 

 macroconidia, and can only be hberated by the decay of the 

 conidiophore. It seems probable that de Seynes' macro- 

 conidia — which occurred singly or in cliains of two or three, 

 were segmented olf from the parent cell within the hyplia, and 



