120 Trausoctions of the Royal Society of South Africa. 
palisade cells. A Meliola species on this host closely resembles M. amphi- 
tricha, and was assigned to this species, as I was in doubt as to whether 
the morphological differences justified describing it as distinct from 
M. amphitricha. This fungus occurs on both sides of the leaf. 
No difficulty was experienced in demonstrating the haustoria of this 
fungus, and in observing their connection with the hyphae on the leaf 
surface. The penetrating filament is •6-'75 /x thick, and stains bright blue. 
It passes through the cuticle, but instead of expanding into a spherical 
vesicle in the epidermal cell, it traverses the epidermis and penetrates into a 
palisade cell, or the first cell of the mesophyll encountered, according to 
whether the fungus is growing on the upper or under surface of the leaf. If 
a sclerenchyma fibre is encountered it pierces through it and so reaches a 
chlorophyll-bearing cell, where it expands into a thin-walled, spherical, 
uninucleate vesicle. The fungus, therefore, is obviously a distinct species 
from M. ampliitriclm. It was suggested that the character of the leaf might 
in some way be responsible for the form of the haustoria. Two other species 
of Meliola occur on Olea laurifolia, and these were examined in order to 
discover whether they produced the same form of haustorium. 
Meliola petiolaris Doidge occurs chiefly on the petioles and on the under 
sides of the leaves, but often spreads somewhat from the lower side over the 
upper margin. On the lower surface the fungus has haustoria similar to 
those of 31, amphitricha, consisting of a fine filament penetrating the cuticle 
and a small, spherical vesicle, about 3 p diam., in the epidermal cell. Near, 
the edge on the upper surface, where the cuticle is much thicker, the haustoria 
are similar in character, but the penetrating filament is stouter and brown- 
walled. This change in the character of the penetrating filament appears to 
be correlated with the thickness of the cuticle, and is very unusual ; in every 
other case the form of the haustorium has been found constant for any given 
species. Of all the specimens examined this was the only species, with a 
vesicle in the epidermal cell, in which the penetrating filament retained the 
brown colouring of the wall of the parent hypha. Maire mentions two 
species, Meliola, hrasiliensis var. sanguineo maculans, and M. amphitricha on 
Schinus sp., which have this peculiarity, and considers that in hosts with a 
thin cuticle the tube traverses the cuticle unchanged, but when the cuticle is 
thick the tube decomes a very fine, filiform tract with hyaline walls. In the 
majority of cases I have found that there is no relation between the thickness 
of the cuticle and the nature of the wall of the penetrating filament, which 
appears to be a specific character. In the case of M. petiolaris the tendency 
is for the filament to be brown-walled and stouter where it penetrates the 
thicker cuticle. 
It will be noticed that Maire found a brown penetrating filament in leaves 
of Schinus attacked by M. amphitricha, whereas on other hosts in South Africa 
this fungus has a fine, hyaline penetrating filament, which stains blue with 
