202 
POPULAR SCIENCE REVIEW. 
of the most universal of favourites amongst flowers : this is 
the rose mould. Attention was directed to this mould, and it 
was described for the first time under the name of Peronospora 
spars a, in the columns of the Gardener’ s Chronicle , in 1862. 
It occurred on a quantity of potted rose plants in a conser- 
vatory. Irregular pale brownish discoloured spots appeared 
on the upper surface of the leaves ; these extended rapidly, 
and in a short time the leaves withered and shrivelled up, and 
ultimately the whole plant perished. A delicate greyish mould 
was to be seen by the aid of a lens, scattered over the under 
surface of the leaves. By the microscope, the branched 
threads, having the tips furnished with sub-elliptic spores, 
were revealed, and an ally of the potato mould found revelling 
amongst the roses. 
Of the remaining British species, one (P. Arenarice), is found 
on the leaves of the three-veined sandwort (fig. 6), another 
attacks the red corn poppy, a third is found on the common 
nettle, one on the brooklime, another on the wood-anemone, 
and another on the figwort. 
Doubtless all the species in this genus are possessed of the 
third means of reproduction, by zoospores, as discovered in 
the potato mould. The fearful rapidity with which this method 
enables them to multiply themselves may account for their 
widely spreading and devastating power. No other genus of 
Fungi can parallel this in the number of species injurious to 
the field or the garden, or in which the injuries inflicted are so 
great and irremediable. 
EXPLANATION OF PLATE. 
Fig. 1. Beaded Brand (. Xenodochus carbonarius), from the leaf of the 
burnet. Greatly magnified. 
„ 2. Burnet Brand (. Aregma acuminatum ), on the three upper leaflets of 
• Poterium sanguisorba , with the yellow sori of the Burnet Rust 
(. Lecythea Poterii) on the lower leaflet. 
„ 3. Spores of the Burnet Rust (Lecythea Poterii). 
„ 4. Spore of Burnet Brand (. Aregma acuminatum). 
„ 5. Strawberry Brand (. Aregma obtusatum), and Strawberry Rust 
(. Lecythea Potentillarum ), intermixed on leaf of Potentilla fraga- 
riastrum. 
„ 6. Spores of the Strawberry Rust (. Lecythea Potentillarum). 
„ 7. Spore of Strawberry Brand (. Aregma obtusatum). 
„ 8. Rose Brand (Aregma mucronatum), and Rose Rust (Lecythea 
Bosce ), on leaflet of cultivated rose, intermixed. 
„ 9. Spore of Rose Rust (Lecythea Bosce). 
„ 10. Spore of Rose Brand (Aregma mucronatum). 
„ 11. Bramble Brand (Aregma bulbosum) and Bramble-rust (Lecythea 
Buborum ), intermixed on leaflet of bramble. 
