196 
Salmon. — On Oidiopsis t auric a (Ldv.), 
again may differ in size if not in shape from the conidia produced on the 
branches of the first and second order 1 . 
Maire describes (6) the conidium as follows : ‘ conidiis cylindraceis vel 
oblongo-cylindraceis, vel ovoideo-oblongis, utrinque retusis, vel apice at- 
tenuate, 50-70 x 15-18 /x \ Two varieties are then founded by this author 
with the following characters : ‘ var. Duriaei (Lev.) A typo differt conidiis 
minoribus, 38-45 x 14-1 8/x’, on Phlomis Herba^venti and P. pungens\ and 
‘var. Zygophylli R. Maire. A typo differt conidiis longe cylindraceis, 57- 
72 x 13-14 /x 5 , on Zygophyllum Fabago. 
An examination of a large number of examples of the conidial stage 
of O. taurica , on thirty-seven species of its host-plants, has convinced me 
that we cannot separate satisfactorily varieties on the characters here given. 
The character, viz. the size of the conidium, 38-45 x 14-18 /x, given as 
distinctive of the ‘var. Duriaei *, does not hold good. I11 an authentic 
specimen of ‘ E. Duriaei Lev.’, from Leveille’s herbarium, at Kew, the 
conidia measure 43-do x 18-23 ^ (Fig. 24). This example occurs on Phlomis 
Herba-venti. In the example on P. puiigens sent to me by Prof. Maire as ‘ E. 
taurica var. Duriaei the largest conidia measure 50 x 20/x; mixed with these 
are remarkably small ones — the smallest I have seen— measuring only 22- 
32 X 13-16 [i (Fig. 22). Conidia as small as 28 x 13 /x occur mixed with conidia 
measuring 60 x 25 jtx on Verbascum Thapsus (Fig. 23) and V. Lychnitis ; on 
Euphorbia lanata (Fig. 38) the conidia range from 35-55 x 14-25 /x, and 
on Cynara Cardunculus from 35-50 x 15-20 /x. Similar cases are quite 
common. 
The characters put forward as distinctive of the ‘ var. Zygophylli ’ are 
even less satisfactory. In the example sent to me by Prof. Maire the 
conidia measure 60-73 x 13-20 /x ; their shape is shown in Fig. 22**. 
In an example on the same host-plant, collected by Dr. O. Stapf 
in Persia, the conidia vary from 45-60 x 14-18 /x, and often depart from 
the cylindrical shape (Fig. 27). Cylindrical conidia measuring 85x1 6 /x 
occur intermixed with oblong-elliptic conidia measuring 44 x 22 /x, on Ruta 
Buxbaumii (Fig. 28). Exactly similar cases are found in the forms of the 
fungus on Asclepias curassavica (Fig. 29), Nepeta podostachys (Fig. 34), 
Capparis herbacea , Psoralea bituminosa , and Passerina annua (Fig. 36). 
On certain host-plants, however, we do find a well-marked, constant, 
and distinctive variation in the shape of the conidium. I first met with 
this in an example, in the conidial stage only, sent to me by Prof. L. M. 
Underwood, from the Herbarium of the Columbia University, labelled 
1 Scalia says of Oidium gigasporum , 1 Conidiis catenulatis cylindraceis vel fere ovalibus, apicali 
sursum acntato, caeteris utrinque truncatulis,’ and ‘ tbe terminal conidium is usually attenuated 
at the apex, and truncate at the base, while the others are cylindrical and rounded at both ends 
and roughly oval/ The same author writes of Oidiopsis sicula , 1 conidiis catenulatis, conidio 
apicali sursum longe papillato, basi truncato, rotundato, caeteris cylindraceis, utrinque rotund ato- 
truncatulis/ 
