366 



UREDINEAE. 



in shape, yellow in colour, and their outer coat is beset with 

 spiny projections. The stalk-cells grow out into elongated tubes, 

 after completion of spore-formation. In the vicinity of the 

 scar of a Caeoma- patch, the twig turns brown and its tissues 

 become permeated with resin, while the tissues underlying the 

 patch die even into the pith. 



Hartig's 1 investigations show that this Q&me Melampsora causes 

 Caeoma laricis on the needles of the larch. Plowright 2 also 

 produced a similar Caeoma-forra from Melampsora bctulina, and 



PIG. 198. Mtlii.iitpxoi-a bitulinu. Teleutospore-sorus, with many of the spores 

 producing promycelia and sporidia (si). ,\ Mycelium ; /), parenchyma ; t, portion 

 of ruptured epidermis. (After Tulasne,) 



succeeded in re-infecting Betula alba from Caeoma laricis. 

 Eostrup obtained Caeoma mercurialis by infecting Mcrcurialis 

 with Mi'], treniidae; yet this may have happened because two 

 different species of Melampsora occurred on the aspen leaves. 

 Klebahn 3 was successful in infesting Pi>i<liis tremula with 

 Caeoma laricis but did not succeed with the birch. 



1 R. Hartig, AUei/em. Forst. u. Jagd-zeitung, 1885. 



2 Plowright, "Impfversuche in. Rostpilzen," Zeitschrift f. Pflanzeiikrankheiten, 

 1891. 



3 Klebahn, Zeitschrift f. P/hnrj iilcnniL-h titen, 1894. 



