NOTES ON THE NOMENCLATURE OF FUNGI 77 



not quite so restricted as was intended. The interpretation of the 

 Eecommendation for fungi is seen, however, on referring to 

 Eecommendation XV bis, where araong the examples we find 

 Puccinia Hieracii and Pucciniastrum Epilobii, and to Art. 49 

 bis, where Polythrincium Trifolii, Diaporthe Ailaiithi, etc., occur. 



III. Cystopus v. Albugo. 



The generic names Cystopus and Albugo are apparently used 

 indiscriminately by mycologists. It seems advisable to point out 

 which name is to be adopted in accordance with the International 

 Eules of Botanical Nomenclature, and to give a few historical 

 facts. 



The first species of the genus which was described was the 

 common " white rust " of cruciferous plants which was named 

 AecicUum candidum by Persoon in Gmelin's Syst. Nat. ii, 1473 

 (1791). The same author in Usteri's Annalen der Botanik xv, 16 

 (1795) proposed the genus Uredo to include this fungus and two 

 new species. Uredo Candida is given as having two varieties 

 " a, dijformis in caule et foliis Thlaspeos Bursae Pastoris Lin., 

 nee non in foliis Tragopogi porrifolii " and " /?, orbicularis minor, 

 in foliis Cheiranthi incani." In describing a specimen on Cap- 

 sella Bursa pastoris, Persoon mentions the distortion of the plant 

 and the bursting of the epidermis, but states that after a few days, 

 when most of the spores have been dispersed, a Botrytis-\\kQ form 

 arises in the same place, and he is uncertain whether this is not 

 to be regarded as the mature form of the described species. This 

 Botrytis {B. parasitica — Pcronospora parasitica Tul.) is described 

 and figured in Persoon's Observationes Mycologicae though the 

 author is apparently still in doubt as to whether it is the cause of 

 the distortion of the host-plant etc. or whether there are two 

 fungi concerned — the result is that Uredo Candida is omitted !" 

 In his Synopsis Fimgorimi (1801), on the contrary, the Botrytis 

 is omitted and the U. Candida again appears. The genus Uredo 

 had by this time grown so much that it is divided into four sections 

 the third of which is Albugo, characterised by having white spores. 

 {Uredo Candida: a, U. Thlaspeos, /?, U. Tragopogi, y, U. Alyssi, 

 Uredo Cheiranthi.) 



Eoussel (Fl. Calvados, ed. ii, p. 47 (1806)) raised this section to 

 generic rank but has only one species. Albugo Candida, of which 

 there is no diagnosis but which is stated to occur on Cruciferae, 

 Hu7iiuliis etc. indicating that the author had not a very clear idea 

 of the genus. Gray (Nat. Arr. Brit. pi. ii, 540 (1821)) also uses 

 the name Albugo generically and includes three species. Albugo 

 cruciferarum {=a, U. Thlaspeos), A, tragopogi and A. p>etroselini. 

 Although Gray had a clear conception of the genus, his names, 

 as in so many other cases, were disregarded at the time. Fries 

 in his Systema Mycologicum does not mention any of the species 

 of " white rust " ; in fact his treatment of the microscopic fungi 

 as a whole is much inferior to that of Persoon. 



* See Jouni. Bot. 1915, 277. 



