South African Perisporiaceae. 
119 
until most of the air was expelled from the tissues, and the portions of leaf 
sank to the bottom of the tube. When the formalin was cold, sections were 
cut with the freezing microtome and transferred direct from the 10 per cent, 
formalin to the stain. 
The stain employed was Gueguen's triple stain (5), which was recom- 
mended by Maire as giving beautiful preparations. This is a solution of 
Sudan III and *' bleu coton " (Bleu C4B Poirrier j in lactic acid, but 
" bleu coton " not being obtainable methyl blue was used and proved to be 
a very satisfactory substitute. The sections were left in the stain for fifteen 
to thirty minutes, and were then mounted and examined in lactic acid. Suc- 
cessful preparations showed the cuticle stained a beautiful clear red, while 
the haustoria and the contents of the external fungus hyphae were stained 
bright blue. 
Some of the species of Meliola are very readily detached from the host, 
and a considerable search had to be made before sections were found show- 
ing the haustoria attached to the hyphae from which they were derived ; 
others adhere more closely and no difficulty was experienced in demonstrating 
the attachment of the haustoria. 
A fairly large number of species was examined, and these will be 
considered separately. 
Meliola amjjhitricha Fr. has been recorded from this country on a number 
of hosts chiefly belonging to the Kubiaceae. The first specimen examined 
was on Sapinclus ohlongifolius. This plant has an ordinary mesophytic 
type of leaf with a fairly thick cuticle on the upper side, the cells of the 
lower epidermis are smaller than those of the upper, and the cuticle on the 
under surface is much thinner. Haustoria were present in great numbers 
in the epidermal cells, and the fungus being amphigenous they were 
observed on both the upper and the lower surface. In every case they 
consisted of a very fine filiform tract — which may be termed the penetrating 
filament — traversing the cuticle and expanding just within the epidermal 
cell into a small spherical thin-walled vesicle. The whole haustorium 
stains bright blue by the method used, and the vesicle has a single central 
nucleus which stains more deeply. This type of haustorium is very similar 
to that described by Harper (6) for many of the Erysiphaceae. On Grumilea 
caffra, which has a very thin cuticle, Meliola amjjhitricha has exactly the 
same type of haustorium as on Sa2)indns ohlongifolms ; a fungus on 
Jasminum streptopus, which is placed under M. amphitricha, was also 
examined and found to have the same type of haustorium. 
The leaf of Olea laurifolia has a thick cuticle on the upper surface and 
edges, the distance from the leaf surface to the lumen of the epidermal cells 
being 12 to 13 (t* ; on the lower surface the cuticle is thinner, the distance 
being only 4"5 to 5 fx. There are sclerenchyma fibres scattered through 
the mesophyll, and occasionally occurring between the epidermis and the 
12§ 
