220 WILSON—PUCCINIA PROSTII AND UROMYCES SCILLARUM. 
ment the areas remain yellowish-brown, but as the teleutospores 
approach maturity an air-space develops under the epidermis, 
and in consequence grey or slate-coloured spots are produced. 
The epidermis finally splits longitudinally, the edges turn 
slightly back and disclose the dark brown mass of teleutospores. 
It is frequently found that a slate-coloured area forms a circular 
or spindle-shaped ring around a yellowish-brown spot (c, Pl. cxliii, 
Fig. 1). Itis evident that in these cases the development is centri- 
fugal, the ripe teleutospores being first produced in the outer part 
of thesorus. Itis quite possible that, in some cases, only spermo- 
gonia are developed in the area, and then the yellowish-brown 
colour remains unchanged. Spots have, however, been often 
found in which spermogonia and groups of young teleutospores 
are intermingled ; and it is probable that, in the majority of cases, 
development commences with the formation of spermogonia 
and terminates in the production of teleutospores. Teleutospore 
sori, not in connection with spermogonia, have also been found. 
The mycelium, which is easily seen in a section of the leaf, 
consists of rather large hyphae, containing yellowish-brown 
granules. The spermogonia are amphigenous, yellowish-brown 
in colour, and flask-shaped, with slightly projecting necks, 
120-140 uw in diameter (PI. cxliii, Fig. 2). The spermatia are oval 
and unusually large, about 10 x5. The teleutospore sori are 
amphigenous (Pl. cxliii, Figs. 3, 4) ; spores brown, scarcely con- 
stricted, covered with rather long hyaline spines 56-62 x 17-19 u ; 
epispore rather thick, 2-3 « ; pedicels variable, shorter or longer 
than the spore, up to 80-u in length, hyaline, deciduous. 
Uromyces Scillarum, Wint. 
Uromyces Scillarum, Wint., the common Scilla rust, has been 
recorded on several species of Scilla and Muscari. In the British 
Isles it is frequently found on Scilla festalis, Salisb., and also 
occurs on Scilla bifolia, Linn., and S. hispanica, Mill.; up to 
the present, however, its occurrence on Muscari has not been 
recorded in this country. . 
It was found in the Royal Botanic Garden in May, forming 
the characteristic yellow spots on the leaves of Muscari poly- 
anthum, Boiss., a species which hitherto has not been recorded as 
a host for this rust. As usual, the sori are often concentrically 
arranged on the rounded discoloured areas. The teleutospores, 
the only kind of spore produced, agree in size and form with 
those found on the other host species ; in size they vary from 
20-26 x 16-18 uw. The characteristic faint lines found on the 
spore wall running from the apex to base can be frequently seen. 
The rust frequently occurs on neighbouring plants of Scilla 
