(406) 



ature, amount of precipitation, or character of the soil have any- 

 direct influence on the distribution of the fungi. It is well known 

 that junipers and cedars occur in diverse climates and on widely 

 different soils, and on hosts in all these varying conditions the fungi 

 thrive. Whether the host occurs in a warm region on a permeable 

 sandy soil or in a colder place on wet marshy ground it is appar- 

 ently equally susceptible to these fungi. The amount of rainfall 

 and the temperature prevailing during the germinating time of the 

 teliospores in the spring might have a seasonal or local influence 

 on the prevalence of the fungi and in this indirect way these factors 

 might have a slight but unimportant bearing on distribution. 



Evolutionary Tendencies 



Regarding pleomorphism and heteroecism there is no evidence 

 brought forth by the investigation of this group which is of sig- 

 nificance except as it is interpreted in the light of our present 

 knowledge of other groups of Uredinales. There is, on the one hand, 

 the view that the species with only two spore-forms (the so-called 

 micro- and lepto-forms) are the most primitive (Dietel, 1899) 

 and that the other species with more spore-forms (hemi-, brachy-, 

 opsis-, and eu-forms) have been derived from them. Along with 

 this view of pleomorphism, goes the generally conceived idea that 

 autoecism is the primitive condition, heteroecism being considered 

 a later adaptation (Klebahn, 1904). Opposed to these views, 

 is the theory that pleomorphism and heteroecism are really the 

 primitive condition of the order (Arthur, 1906, Blackman, 1904). 

 This latter theory assumes that the production of the four spore- 

 forms now known in the full life-cycle (eu-forms) was a very early 

 condition in evolution and that the forms now extant with fewer 

 spore-forms have been reduced by later influences. Similarly 

 autoecism is derived from heteroecism by a reduction process. 



It is not necessary to review here all the observations upon 

 which these views are founded. Neither of the views explains 

 the real origin of the group, but simply attempts to express the 

 trend of evolution since a time when the group attained a more 

 or less definite morphology and a parasitic mode of life. No 

 assumptions need be made concerning what took place prior to 

 this time in order to make out relationships between the various 

 forms as they now exist. We are not so much concerned wth 

 the question as to how these organisms acquired the parasitic 



