GYMNOSrORAXGIUM. 401 



A sharply delined roiiiulisli scar of a light-yellow colour 

 remains after the spores are cast. This is composed of a 

 superficial layer of coloured pseudoparenchyma, with an under- 

 lying scar-tissue of characteristic constitution. The latter con- 

 sists of several layers of cork-cells extending from one edge of 

 the scar to the other, separating the cushion from the twig- 

 tissues. This scar-tissue is not broken through next year, but 

 the new sporogenous cushions l)reak (tut through otlier parts 

 (.f the bark (Fig. 236). 



G. confusum Plowright.i (Britain.) This is found on 

 Jiinipirtis ^((hiiia along with G. sahinac, from which it is 

 difficult to distinguish. Pycnidia and aecidia are produced 

 generally on Crataegus Oxyacaiitlia and Cydonia vulgaris, rarely 

 on Pyrus communis. The aecidia on Crataegus resemble those 

 of G. clavariaeformc on the same host, and dehisce by the 

 ruptured apex of the peridium. Tliose produced on Pyrvs 

 communis are distinguished- from aecidia of G. sahiuof on 

 the same host by dehiscing through the open apex of the 

 peridium. 



Infections of Gym. confusum from Juniperus cummunis gave 

 the following resiilts : 



On Host-plant. Authority. 



^ , . , . 1 iivciiidia and aecidia with i , , .,-, • _ „ 



Cydona ndgans, - - M • ^^^,^^^,^^^. ^^^.^.^ . . J K. b ...ci.e, . 



Crataegtis O.vyacaiitlta, - „ „ „ >> 



Pyi'us communiii, - - „ „ „ » 



Cmtaeyns O.njacanth'i^ - .. „ „ Pl..\vi-i,<ilit. 



The following American species of Gyianosporangium have 

 been described:-^ 



On Arl)orvitae or white cedar: 



G. biseptatum Ellis. On twigs and needles of Chnmaecyparis 

 thyoidcs and Lihocedrus decuirens. The aecidia on Crataegus 

 tomcntosa and Amelanchier canadensis. 



' Plow-right, Linnean Sor. Jountal {Botany), 1887. E. Fischer, Zeit-schrift /. 

 Pflanzenkrankheitm, i., 1891 ; with summary of literature. Klebahn, Forst/.- 

 iiaturu-h'i.i. Zeit^chrtft, ii., 1893. 



2 E. Fischer (/or-, at. ). 



•'Farlow, The Development of the Gymnosporannia of the United State", 188(i, 

 and other papers. Thaxter in various ijapers on Gymnosporangia, 1880 to 

 1891. Halsted (Beporf on Veyetahle Patholoyy for 1888, U.S. Dept. of Agri- 

 culture) gives a nxiime, with description and figures of G. marropm and 

 treatment for orchard-rust. Fischer, Zeitschrift f. PJlanzenkrankheiten, i., 1891. 



2C 



