ON THESIUM 229 



/Ecidia on Geranium pusillum, and possibly also on G. molle, 

 G. rot a ml! folium; uredo- and teleutospores on Polygonum Con- 

 volvulus, August and September. Uncommon. (Fig. 176.) 



The connection of the secidium on the first-named host and the 

 Puccinia on Pol. Convolvulus has been experimentally demonstrated by 

 Tranzschel. It is possible that the same parasite also attacks P. dume- 

 toruin, P. Persicaria and others. The recidium is not known for certain to 

 have occurred in Britain. The teleuto-sori of P. Polygoni-Convolvuli are 

 distinguished from those of P. Polygo?ii-amphibii by their compact 

 pulvinate form, and by being soon uncovered by the epidermis, while the 

 spores (perhaps in consequence of that) are much darker at the summit, 

 and the apex, if conical, is less often oblique. According to Sydbw these 

 distinctions, however true they may be of the European forms of the 

 species, do not avail when the extra-European forms are considered. In 

 the Monographia, therefore, the two species are united, and only culture 

 experiments will be able to decide the question. 



99. Puccinia Thesii Chaill. 



yEcidium Thesii Desv. in Journ. de Bot. ii. 311 p.p. Cooke, Handb. 



p. 537 ; Micr. Fung. p. 195, pi. 3, f. 50—1. 

 Puccinia Thesii Chaill. in Duby, Bot. Gall. ii. 889. Cooke, Handb. 



p. 495 ; Micr. Fung. p. 204. Plowr. Ured. p. 145. Sacc. Syll. 



vii. 602. Sydow, Monogr. i. 585. Fischer, Ured. Schweiz, p. 300, 



f. 219. 



Spermogones. Amphigenous, numerous, amongst the aecidia. 



Fig. 177. P. Thesii. Teleutospores, from a Surrey specimen. 



jEcidiospores. /Ecidia amphigenous, scattered uniformly 

 and rather thickly over the whole leaf-surface, seldom in roundish 



