GYMNOSPORANGIUM. 



389 



fissure-like pores in place of bordered pits. The wood-elements 

 in cross-section are no longer round but polygonal ; the bast 

 becomes very irregular, parenchyma grows rapidly, bast fibres 

 remain thin-walled and have no longer a straight course. The 

 mycelium fills the bast and rind, forming masses in the inter- 

 cellular spaces ; it is easiest found in the tangential section. 

 On tlie fall of the club-shaped sporophores, a scar is left and 

 under it will be found a layer 

 of cork many cells thick ; when 

 new sporophores are formed in 

 later years, they seldom break 

 through the cork layer, but 

 emerge tlirough some new por- 

 tion of the bark. 



Gymnosporang-ium tremel- 

 loides Jlartig^ on J ualpirus, rum- 

 muiiU. The sporocarps of this 

 species occur on the branches 

 and needles; its aecidia — Roc- 

 Mclia peyiicillata — on leaves of 

 apple (Fi/rns Mains), Pyrus Aria 

 and P. Chamacmesjnlus. This 

 Rocstdia is externally very like 

 that of G. clavaricu'formc on 

 Crataegus. The markings on the 



cells of the peridium consist of somewhat wavy lines, not of 

 short rod-like markings as in R. cornuta ; and the cells of the 

 peridium are joined by a characteristic hinge-joint (Fig. 224, 

 19 and 20). 



The mycelium perennates in the rind of Junijjcru.'i communis 

 and J. imna, causing thickening of the twigs and a premature 

 death of the distal portion above the swellings. The chocolate- 

 brown velvety spore-cu.shions break out between the bark-scales 

 on the swollen places, about the middle of April (Fig. 225, l). 

 The teleutospores are two-celled, the earlier formed ones being 

 short, ovoid, and slightly pointed at each end, while the 

 later ones are thinner-walled and often more elongated 

 (Fig. 225, 6-10). 



Fici. 'iili.— Tangential longitudinal sec- 

 tion through the parenchyma-zone of 

 Fig. -220. (After Woernle.) 



^Hartig, 7>>/»ease.s of Trees, English edition, 1894. Dietel, For-^tlich-iiatur- 

 vAss. ZeiUchrifl, 1895, p. 348. E. Fischer, Heihcujia, 189.5, p. 1. 



