88 BASIDIOMYCETES 



sive stages on the same host. We have a famihar instance in 

 the Northern States in the common mandrake or may-apple {Podo- 

 phyllinn peltatut)i)\ in the spring brilhant yellow cluster cups appear 

 on the young leaves in certain definite centres of infection ; from 

 these the spores are scattered to other mandrake plants and in 

 early summer their 1)iight green leaves become mottled with yel- 

 lowish or brownish areas in which the teleutospores of the fungus 

 soon appear. {PL 6. f. 8.) In this rust there are no summer spoi es 

 {Credo) sincQ their function is carried on by the aecidiospores. In 

 other rusts as in Puccinia graininella teleutospores and aecid- 

 iospores are not only produced on the same plant, but from the 

 same mycelium. {PL 6. f. 7j.) 



Not all rusts possess aecidia. In some the teleutospores rarely 

 form owing to the fact that the mycelium has become perennial 

 probably in underground parts — a departure from the usual 

 habit of the fungus in which the mvcelium is commonlv confined 

 to a limited area not far from the point where the sorus is formed. 

 With the aecidia or sometimes independent of them a series of 

 structures are formed whose function is not known. These are the 

 spermogonia which appear to the naked eye as blackish points 

 usually on the opposite side of the leaf from the cluster cups. In 

 section they show pycnidia-like cavities from the mouths of which 

 small tufts of hairs emerge ; within, the spore-like bodies {sper- 

 matid) are developed at the ends of slender mycelial threads. 



The various habits of production of one, two or three forms of 

 reproductive bodies has led to the establishmer t of subgeneric 

 groups in some of the larger genera. For instance, in the genus 

 Puccinia the following groups have been proposed : ^ 



EuPUCCiNiA : producing aecidia, uredospores and teleuto- 

 spores. 



* Since in our own country alone there are some one hundred and 

 twenty-five aecidial forms whose relations to our 300 species of Puccinia 

 and 100 species of Uroniyces are unknown, the position of any given spe- 

 cies in these groups is, to say the least, very uncertain. There is abundant 

 opportunity for botanical students everywhere to insUtute a careful study of 

 the relations of the aecidia to teleutosporic forms. The study must be 

 taken up first in the field to establish suspicions from proximity of growth 

 and then to supplement field work with actual culture (inoculation) ex- 

 periments. 



