1 88 Salmon . — On Oidiopsis taurica {Ldvl), 
sometimes monopodial (and repeated in the branches of the first and second 
order) and more or less definite ; at other times it is apparently quite 
indefinite. From certain cases observed, it appears that mycelial hyphae 
may grow out from the conidiophore. The conidia are borne singly at the 
apices of the main axis and lateral branches. It appears, from certain dried 
examples which I have seen, that after the first conidium has been abstricted 
another may sometimes be produced l . In this character the present fungus 
resembles Phyllactinia (see ( 5 ), p. 494). The conidium is extremely 
variable in size and shape, even when taken from the same host-plant, as 
can be seen by referring to the figures in Plates XIII and XIV. On 
some hosts, however, the conidium shows constant and distinctive characters 
as regards its shape. The variations shown by the conidium in examples 
of the species on different host-plants will be dealt with fully below. 
As mentioned above, the mycelium is at first wholly internal. The 
endophytic hyphae are abundant just below the epidermis, where they run 
freely in the intercellular spaces, and often form a kind of thin weft. 
Besides winding in and out among the intercellular spaces between the 
cells of the spongy parenchyma, the hyphae not infrequently extend to the 
intercellular spaces between the cells of the palisade tissue. In those cases 
where stomata are frequent on both surfaces of the leaves, the intercellular 
mycelium runs throughout the intercellular spaces of the mesophyll, and 
sends out the conidiophores and the hyphae of the external mycelium 
through the stomata of both surfaces to an equal extent. The hyphae 
of the endophytic mycelium are septate, from 4 to 6 /x in diameter, and are 
sometimes tortuous and branched, with numerous free ends, while they 
sometimes run nearly straight for considerable distances in the intercellular 
spaces just below the epidermis (Fig. 3). Often mesophyll cells, here and 
there, become closely invested by a weft of hyphae. From the intercellular 
hyphae small haustoria, more or less globular in shape, are sent into the 
mesophyll cells, both those of the spongy parenchyma and frequently also 
those of the palisade tissue. I have not observed any cases in which the 
epidermal cell has been entered for the production of a haustorium by 
penetration of the inner wall. 
In the later stages of the conidial condition, the fungus becomes more 
evident on the surface of the host-plant, and approaches in habit the other 
members of the Erysiphaceae, because mycelial hyphae now emerge in 
1 The statements of authors with regard to this point have been as follows. Sorokine (in 
Revue mycolog., 1889, p. 146), speaking of Erysiphe Saxaouli [ = E. taurica], says, ‘II n’y a qu’une 
seule spore sur chaque hyphe verticale.’ Scalia writes of Oidiopsis sicula , ‘ conidiis catenulatis, 
facillime secedentibus,’ and states that when the conidiophore is branched ‘a chain of conidia, in 
the manner of Oidium , is produced on each branch.’ The same author in his diagnosis of Oidium 
gigasporum says, ‘ conidiis catenulatis,’ and also, ‘ the conidia become abstricted directly they are 
formed.’ Maire observes, ‘ Les conidiophores donnent naissance a leur sommet a un petit nombre 
de conidies qui se forment et se desarticulent successivement ; quelquefois il ne se forme qu’une 
seule conidie.’ 
