110 I. WAHL 



conditions which would be lethal to fungi which lack the 

 capacity to produce such forms. Venkat Ram^^ cited evidence 

 that antibiotics produced by bacteria induce chlamydospore 

 formation in Fusarium solani. 



Several types of treatment have been employed to break 

 dormancy. One of the methods is based on simulation of 

 conditions prevailing in natural habitats, and consists of altering 

 temperatures and humidities, a procedure widely used for rusts 

 and smutsi' ^. It is postulated that by freezing and thawing, 

 drying and wetting, the permeability of the spore wall becomes 

 increased. Similar changes in permeability of the cell wall have 

 been reported with UstUago striiformis submerged in dung 

 infusion^^. Another method involves treatment with various 

 chemicals — inorganic and organic acids, chloroform, ether 

 benzaldehyde, siHcylaldehyde and others^' ^. In this connection, 

 Stakman and Han'ar^ pose a fundamental question and 

 commented upon it as follows: 'How do the various classes of 

 chemical substances produce their effect? They are an aid to 

 experimentation, but how does nature substitute for them? In 

 some cases at least it has been shown that the effect is not on the 

 permeability of the spore wall. Many of the substances are 

 known to reduce the surface tension of water, and it is possible 

 that they may act on the content of the spore in such a way as to 

 permit greater hydration.' The author of this paper failed so far 

 to induce germination in teliospores of oat stem rust despite the 

 fact that water could be introduced into the spore cells. 



High temperatures have also been successfully employed in 

 breaking dormancy of resting spores or chlamydospores^' i^. 

 Goddard and Smith^' attribute the effect of high temperature 

 shocks to activation of carboxylase. The respiratory block is 

 then the inactivity of this enzyme. 



It should be pointed out that activation achieved by high 

 temperature shocks can be duplicated by furfural treatment^^' i^. 

 These methods achieve cell activation by putting into operation 

 different biological mechanisms, e.g., heat treated spores of 

 Neurospora crassa can be deactivated by exposing them to 



