GYMNOSPORANGIUM. 387 



may be as long as 10 m.m. and are bent like a born (Fig. 219). 

 A similar case is described by Barclay^ in wbich the peridia 

 of aecidia on Rhamnus dahurica were very long if produced 

 in dry weather, but short if in moist weather.^ 



The aecidiospores are shed during the early part of June, 

 and germinate at once on the bark of young juniper-twigs ; 

 the mycelium growing thence into the spurs or branches to 

 spread and hibernate. Teleutospores which germinate on 

 Pomaceae other than species of Crataegus have apparently a 

 normal mycelium, but produce pycnidia only, or aecidia with 



Fig. 220. — Cross-section through a swelling caused by GymnosporangiwTi on 

 Juniper-stem ; parenchyma with large cells and thin walls is present in abnormal 

 quantity. (After Woernle.) 



peridia differing from those on Crataegus. My own experiments 

 on the quince and mountain ash regularly produce pycnidia only. 

 Wakker^ summarizes the anatomical changes induced in 

 deformed shoots of hawthorn as follows : cork, collenchyma, 

 sclerenchyma, and chlorophyll are not formed, lignification of 

 the cells of medullary rays no longer takes place, and there 

 are few intercellular spaces. Interfascicular cambium is not 

 formed, while activity of the intrafascicular cambium is suspended 

 at an early period, so that the vessels remain incompletely 

 developed. The epidermis is irregularly formed and liable to 

 rupture. All parenchymatous cells undergo enlargement in a 

 radial direction. Starch is stored up in large quantity, and 

 the formation of calcium oxalate is diminished. 



^"On the life-history of Pticcinia coroiiata var. himalensis," Trans. lAnnean 

 Soc, London, 1891. 



^ This probably is the explanation of the long peridia obtained by Peyritsch 

 and described by Magnus (Berichte d. naturwiss. medic. Verein, Innsbruck, 1892-93). 



^ Pringsheim's Jahrbuch, 1892. 



