372 A. Barclay — List of the Uredineee occurring [No. 3, 



yellow around it (Fig. 2, PI. XV ) and pale rosy red beneath (Fig. 1, PI. 

 XV.). The patch is concave on the upper or red surface, the under 

 surface being correspondingly convex, and on this latter surface only 

 are the ^cidia produced. Generally only one patch is to be found on a 

 single leaf, though I have seen as many as six. The patches are usually 

 very uniform in size, generally measuring about 6 m.m. in a diameter. 

 The centre of the under surface of the patch is occupied by a number 

 of spermogonia, while around it the secidia are grouped more or less 

 irregularly. A few spermogonia, however, emerge from the upper 

 surface also. This -<:Ecidium, therefore, in its general characters 

 already resembles that described above on Euphorhia cognata, but 

 differs notably in the aecidia being isolated cups, whilst in Euphu- 

 bia we may imagine that the several cups have all fused together into 

 one large circular secidial fruit. The peculiar arrangement of the 

 mycelium, however, in layers so characteristic of M. Euphorhiae 

 is not found here. The mycelium ramifies generally among the 

 cells as in other secidia. The palisade-cells are not disarranged or 

 deformed in anj'- way, but the spongy tissue cells are hypertrophied and 

 proliferated. The thickness of the leaf where invaded and where ripe 

 aecidia were borne was in one instance 0*334 m.m., whilst the normal 

 thickness was 0*138 m.m. The spermogonia are very small and super- 

 ficial, as in M. Euphorhiae. They are insinuated between the epidermis 

 cells and measure about 44 /x in width and 25 to 30 /a in depth. The 

 secidia when fully ripe measure about 0265 to 0"248 m.m. in width and 

 0-233 to 0-217 m.m. in depth. 



The cecidiosjpores are round, oval (Fig. 11, PI. XV.), colourless, or very 

 pale brown, and measure, when just wetted, on an average 21-6 x 18-4 />t, 

 varying from 20 X 16 to 24 x 20 /x. They are given off in rows with- 

 out any intermediate cells. The peridial cells are flat and irregular in 

 shape, imbricate in arrangement, and measure from 18 to 24 /* in 

 diameter (Fig. 10, PL XV.). They are beset with small ridges or 

 tubercles. The mode of germination of these aecidiospores is exactly 

 like the peculiar germination of the spores of Monosporidium Euphor- 

 hiae. The spores germinate very readily in water, throwing out a 

 long non-septate tube, when the empty spore wall is seen to be 

 beset very densely with minute tubercles. After lying in water 24 to 

 36 hours, a secondary spore is formed at the extremity of the germ 

 tube (Fig. 13, PL XV.) just as I have described it in the case of Euphor- 

 bia. This secondary spore or sporidium is separated off from the 

 germ tube by a septum, but never falls off altogether from the tube. 

 In a cultivation of 48 hours' duration, I saw numerous secondary spores, 

 and several of them, while still attached, had commenced to germinate, 



