96 A. Barclay — A Descriptive List of the Uredineoe [No. 2, 



The lower surfaces of the leaves exhibit a few or a very great many 

 slightly paled circular areas on each of which a minute pustule is 

 formed, containing yellowish brown uredospores. The invaded areas 

 are not in the least thickened. When a leaf is not excessively attacked 

 the uredo pustules frequently exhibit a marked circinate arrangement, 

 two circles around a central pustule. 



The teleutospore stage consists in the gradual production of Pucci- 

 nia spores in the uredo pustules, which latter then enlarge very greatly. 

 The teleutospore beds are well raised dark brown compact masses. If 

 a leaf bearing teleutospore beds be placed in a moist chamber the beds 

 swell very noticeably, and become light brown in colour. This swelling 

 is due to the swelling of a gelatinous sheath enclosing the stalks of the 

 teleutospores. 



The mycelium bearing uredo- and teleuto-spores does not contain 

 orange red oil globules, does not form hausteria, and does not give rise 

 to any hypertrophy of the host's tissues. That bearing aecidia contains 

 conspicuous coloured oil globules and gives rise to considerable hyper- 

 trophy of the host's tissues ; but still does not form haustoria. 



The uredospores are oval or pyriform, pale yellow, and beset exter- 

 nally with very prominent spines. Among them are a few club-shaped 

 paraphyses. They are formed singly on short stalks. The fresh spores 

 measure on an average 46 "5 x 3r7/x. The epispore is thickened at the 

 free end. They do not germinate readily in water, and I have con- 

 sequently not observed their germination with accuracy. 



The teleutospores are pale yellow, with long stalks surrounded with 

 a gelatinous sheath. The free end is thickened. They vary in length 

 from 74*0 to 50*8/>i : the upper cell varies from 38 x 16 to 25 x 15/x, 

 and the lower from 36 X 16 to 25 X 15/x. The spore is slightly con- 

 stricted at the septum, and measures about 14/x in breadth. They are 

 firmly adherent. The epispore is smooth. When the stalk is swelled 

 in water the thin central axis is clearly defined as in Gymnosporangium, 

 The spores germinate by forming two usual promycelia, but instead of 

 forming sporidia on sterigmata, the four cells of each promycelium 

 separate from one another, and apparently represent sporidia. These 

 detached cells measure from 14 X 8 to 18 X 11/x. I never observed 

 these cells germinating. At the time I wrote the paper referred to 

 above I had never witnessed any variation from this mode of germina- 

 tion. At that time all my cultivations were made in hanging drops of 

 water in a confined atmosphere. Recently, however, I caused the te- 

 leutospores to germinate in water in a watch glass, in a large moist 

 atmosphere (as recommended by Plowright), and then the usual spori- 

 dial formation took place. The sporidia are oval and orange red and 

 measure from 10/x in diameter to 18 x 8/u,, 



