ON IRIS 



231 



ovate, ochraceous-brown, echinulate, 20 — 35x16 — 26 jjl; epi- 

 spore thick, with 2 — 4 (or more) germ-pores. 



Teleutospores. Sori hypophyllous, few and irregularly scat- 

 tered, sometimes confluent, oblong, 

 compact, persistent, soon naked, 

 black : spores clavate or oblong, 

 much thickened (up to 14 //,) at the 

 summit and rounded, less often 

 conical or truncate, gently constric- 

 ted, usually attenuated below, 

 smooth, fuscous-brown, darker above, 

 30 — 52x14 — 22yx; pedicels brown- 

 ish, thick-walled, persistent, about 

 as long as the spore. 



Fig. 178. P. Iridis. Teleuto- 

 spores, on I. Pseudacorus. 



On Iris foetidissima, I. Pseuda- 

 corus, and on many cultivated 

 species of Iris. Not common. 

 May — October ; the teleutospores 



may be found on the old leaves until the following spring. 

 (Fig. 178.) 



The uredo-stage is most abundant and assumes various characters, 

 especially as regards the formation of spots ; when present these are 

 conspicuous, oblong or oval, and yellowish, often with a greenish-brown 

 circumference. In that case the leaf looks remarkably variegated. 



Plowright considered that the form which occurs on our cultivated 

 Irises is different from that on our native species, because he could not 

 find any teleutospores in the former ; other authors consider them as the 

 same, because the teleutospores on many species are difficult to find, and 

 appear only on dying leaves, especially towards the base, at the end of the 

 season. One can easily recognise them by their being naked ; for in this 

 species, contrary to the usual state of things, the uredo-sori remain long 

 concealed by the epidermis and the teleuto-sori soon become uncovered. 

 The uredospores are very thick-walled ; they can survive the winter and 

 reproduce the fungus in the spring. 



This species might be hetercecious : no experimental cultures appear 

 to have been made. It will probably turn out to possess several biological 

 races, for it has been recorded on more than thirty-five species of Iris. 



Distribution : Europe, Asia, North America. 



