ENDOPHYLLUM EUPHORBIAE-SYLVATICAE 509 



of Psalliota campesfris is looked down upon through a cover-glass, 

 one sometimes sees the drops begin their excretion normally, as 

 shown for the right-hand spore in Fig. 205, D. Then the drops may 

 step up and continue growing, as in the left-hand spore of D and in 

 E. Growth may continue until the two drops touch and join, as 

 at F. Further growth may result in the formation of a large 

 globular drop on the tops of the two sterigmata, as shown at G. 

 In Psalliota campesfris, spores which excrete these abnormally 

 large drops are never discharged. It seems clear that the abnormal 

 excretion of drops from the hila of spores in the Hymenomycetes 

 finds its parallel in the Uredineae, at any rate in Puccinia graminis. 



From all the observations which have been recorded in the 

 foregoing pages on Puccinia graminis, we may conclude that both 

 the normal and the abnormal phenomena accompanying the dis- 

 charge of the spores are similar to those which are characteristic 

 of Hymenomycetes. The mechanism of spore-discharge in the 

 Uredineae and the Hymenomycetes is doubtless identical. This 

 deduction, from physiological studies, serves to strengthen the belief 

 in the close genetic relationship of the two groups. 



The nature of the force which brings about the discharge of 

 the spores is just as much a mystery in the Uredineae as in the 

 Hymenomycetes. That there is some powerful force which can 

 be applied just beneath the hilum is shown by the fact that so 

 relatively large a mass as that shown in Fig. 205, A, d, can be shot 

 away a considerable fraction of a mm. from the top of the slender 

 sterigma. 



The Discharge of Basidiospores in Endophyllum Euphor- 

 biae-sylvaticae. — The genus Endophyllum is unique among the 

 Rust Fungi in that the aecidiospores, on germination, instead of 

 producing a mycelium, at once give rise to basidia. It is believed 

 by Grove ^ that the genus is a primitive one and that, during its 

 phylogenetic development, it has never possessed a uredospore stage ; 

 but Dietel^ and others look upon it as a product of reduction 



1 W. B. drove, " The Evolution of the Higher Uredineae," The New Phyto- 

 hn/lsf. vol. xii, 1913. p. 100. 



- P. Dictol. in a review of W. B. Grove'.s " The British Rust Fungi,"' Mi/co- 

 lofjisches Centmlblalt, Bd. IV, 1914, pp. 209-210. 



