BRITISH HETER(ECIOUS UREDINES. 99 
remembered, however, that, as Reess* pointed out in 1870, 
G. fuscum has two forms of teleutospore, one much darker in 
colour than the other and less abundant. I find these two spore- 
forms constantly mixed together in the same jelly-masses, and that 
the paler spores germinate at once upon being placed in water, 
but that the darker ones do not. G. fuscum gave rise, in Exp. 
522, to the Restelia on Mespilus germanica; but, owing to the 
difficulty of obtaining suitable Mespilus-plants, I have not been 
able to repeat the experiment. 
With Pyrus Malus aud Pyrus Aucuparia, in the small number 
of cultures I have made, my results, like those of previous 
observers, have been negative. . 
Unsatisfactory as these observations are from one point of 
view, yet it is desirable that they should be put upon record. 
Prof. Farlow, who is engaged upon the study of the life-history 
of the American Gymnosporangia, which species are far more 
numerous there than is the case in Europe, has also found it 
exceedingly difficult, so that I have the less. compunction in 
publishing the results of my own observations. 
GYMNOSPORANGIUM FUSCUM. 
No. | Infecting material. Plant infected. ; en Den 
2. mnospor. fuscum. | Pyrus communis. 19 April | 6 May 
6. “y nn ^ ” 7 » 7 April 24 April 
10. » LE » » 14 April 6 May 
25, LE ” ” ” 11 May 11 June 
128, » » my 29 April | -— 
127. » ” ” ” ” — 
185. ” ” ” ” 12 June 2 July 
186. ” » „ ” ” ” 
507. ” » » » 30 April mr 
535. » DE » ” 12 May — 
569. » ” » » 3 June —— 
3x -) » » » » 18 May 
354. » " Crategus Oxyacantha. ” 1 June 
355. | » » » » » 7 June 
356. » » Pyrus Malus. » 
ux.) ” ?,» P. Aucuparia, tha 25 Á " 7 May 
J3. » » Crate, ıyacantha.| 25 Apri 2 
494. » » » At 2 » 5 May 
495. ” ” » ” ” 10 May 
496. » » Pyrus communis. " — 
991. | » » Crategus Oxyacantha.| [29 April | 7 May 
592. , » p Pyrus communis. "E 
593, ” » Crategus Oxyacantha. {> April | 9 May 
594, » » Pyrus communis. » 
* Reess, Abh. d. naturf. Ges, zu Halle, 1870, p. 65. 
