144 MR. А. BARCLAY ON THE LIFE-HISTORY 
tissue, from the epidermis to the margin of the central circle of fibrovascular bundles, 
was 0:25 millim., it was from 0:88 millim. to about 1 millim. opposite the centre of the 
teleutospore beds. Further, in the unaffected parts of this tissue isolated small fibro- 
vascular bundles (leaf-traces) may be seen, but in affected areas these: have almost 
entirely disappeared; so that between the bases of the fruit-bodies ( peridia) and the 
central fibrovascular system there is a uniform mass of hypertrophied cortical paren- 
chyma cells. These cells are much enlarged, for whilst the normal cells in transverse 
section measure about 2919, ог 16 12 и, the cells amongst the mycelium measure 
up to 76X63, or even more. These hypertrophied cells, in transverse section, are 
round or oval in outline; but between zecidial cups they are elongated, measuring about 
1134 in length by 315, in breadth (Pl. XLIX. fig. 15). Between these elongated 
cells the mycelial filaments may be seen in great abundance. Although the myce- 
lium gains entrance sparingly into the central parenchymatous tissue of the stem, it is 
not perennial. 
When sections are made through young ecidial patches, all the peridia will be found 
to contain гесійіоврогев only; but in somewhat older patches it will be seen that, whilst 
the central peridia contain teleutospores, the marginal ones contain only eecidiospores, and 
a few intermediate between these will be seen to contain both, though in the last case 
neither spores in their fullest development (Pl. XLIX. fig. 16) When the production 
of zecidiospores ceases within a given peridium, the whole layer of basidia appears to be 
forced upwards by the developing bed of teleutospores—in other words, there is no con- 
current growth of әесійіоврогев and teleutospores in any peridium ; but, on the other 
hand, there is no pause between the cessation of the production of гесійіоврогев and the 
development of teleutospores. The exact way in which a substitution of teleutospores 
for zecidiospores takes place is as follows :— When a sufficient number of zcidiospores 
has been formed in a given peridium, the centre of the hymenium producing them is 
upheaved, and very shortly broken through by the developing teleutospores. A section 
through the middle of an æcidial cup at this time shows, therefore, a crop of young 
immature teleutospores, flanked on either side by old әесійіоврогев (Pl. XLIX. fig. 16). 
The crop of teleutospores increases very rapidly radially, and so quickly throws off the 
whole hymenium which bore the eecidiospores that in many sections, while a more 
centrally placed peridium in а patch may be seen bearing teleutospores only, the adjacent 
peridium may still be full of cecidiospores. Thus teleutospore formation is not only 
centrifugal in each peridium, but is also so in respect of the whole of the peridia on 
a patch of invasion. 
The teleutospores are much greater in size than the ecidiospores, and the peridia, when 
they come to contain them, increase much in breadth: А young eecidial спр filled with 
ripe zecidiospores was found to measure 0:189 millim. in diameter, and one in the'same 
preparation, containing old æcidiospores, 0:315 millim. in depth and width, whilst an 
old eup with mature teleutospores measured 0:31 millim. in depth and 0:548 millim. in 
width. These measurements show, therefore, that there is also a centrifugal development 
in each peridium from first to last. 
