Adams: Darluca on Peridermium Peckii 311 



I have been unable to find in the literature where Darluca filum 

 has been reported on any species of rusts attacking Gymno- 

 sperms. The writer collected material of Peridermium Peckii 

 on Tsuga canadensis at Charter Oak, Center County, Pa., for 

 study in the early stages of the development of the aecidium. 

 The material was collected May 20, 1917 and at this time it was 

 possible to find infected leaves with immature as well as sporu- 

 lating aecia. The young infected leaves are easily recognized by 

 their yellow appearance. At this time there was no evidence of 

 Darluca growing on any of the rust infected leaves. The para- 

 site was only recognized on examining sections through rust in- 

 fected leaves of material collected in 1917- 



During the spring of 1919 rust infected leaves of hemlock were 

 carefully examined and in several instances mature aecia were 

 found which were parasitized with Darluca. The black pycnidia 

 could be recognized in the sori but not as conspicuous as found 

 on other species of rust. The infection can be easily overlooked. 

 Additional material, was collected and fixed for further study. 



On the leaves of hemlock, Peridermium Peckii forms two rows 

 of conspicuous cylindrical aecia which are erumpent on the under 

 surface. The pycnia develop subcuticularly and frequently were 

 formed on the upper surface but more commonly on the under 

 surface of the needle. 



The mycelium of the rust is distributed throughout the leaf 

 and the aecial primordia originate between the fibro vascular 

 bundle and lateral resin duct. It has been observed that the aecia 

 rupture at a stoma possibly because of least resistance. The 

 mycelium of the parasite is similar in size to that of the rust but 

 can be distinguished easily by the smaller nuclei, less cytoplasmic 

 contents and sparsely septate mycelium. 



Infection by Darluca may occur with the aecial primordia or 

 mature aecia. When the primordia of the aecia are infected con- 

 siderable disorganization of the rust mycelium occurs. The 

 pycnidia of the parasite appear to suppress development by en- 

 croachment. The hyphae making up the aecial primordia do not 

 show the normal nuclei or protoplasmic contents. These hyphae 

 by their strong affinity for the stain and poor stainable contents 



