

has called attention to its great importance. It ia clear, 

 at any rate, that the problem of temperature influence upon 

 organisms falls readily into two fundamentally related, hut 

 superficially different, portions, one dealing with maintain - 

 ed temperature and the other witJb, fluctuating temperatures. 

 Practically all of tne controlled experimental work thus far 

 published ieals with the first portion of the problem and it 

 is in this same catagory that the present investigation lies. 

 Indeed, it seems unwise to attack the problems related to 

 fluctuating temperature until a more thorough appreciation 

 has been gained concerning the general principles underlying 

 the influence of maintained temperatures upon vital processes. 

 It was with the aim of throwing additional light on some of 

 the principles underlying the effects of maintained tempera- 

 ture on the growth of certain fungi, that tne investigation 

 reported in this paper was undertaken. 



Filimentous fungi were used, because they are compar- 

 atively simple organisms whose growth rate may be easily 

 measured, because they lend themselves readily to culture in 

 darkness, and because each cell being in direct contact with 

 all features of its environment , their relation to tneir sur- 

 roundings is simple and close. The four forms, Pythjacystis 

 citrophthora Sm. and Sm. , Ihytophthora terrestria Snerbakoff , 

 Phomopsis citri lawcett, a.r.d Eiplcdia natalensis Evans were 

 used, all of them being parasitic on citrus trees. These 

 were known to grow well on certain prepared media and 3ome 

 evidence was at hand showing that they differed from one an- 



