FUNGOID PESTS OF CULTIVATED PLANTS. 57 



are short and olive, whilst the conidia are long and narrow (60-100 x 4 ft), 

 attenuated upwards almost to a point, and divided transversely by eight or 

 nine septa. 



Primrose Rot-mould. 



Pcronospora Candida (Fckl.), PI. IV. fig. 70*. 



Although of rare occurrence in this country, the above rot- mould has 

 made its appearance on wild plants, without visiting and inflicting damage 

 on cultivated species, except on rare occasions. 



White mouldy spots appear on the under side of living leaves 

 which are conspicuous by their snowy whiteness, although not very 

 dense. Slender erect threads arise from the creeping innate mycelium 

 which are many times branched in the upper portion in a forked 

 manner. The final branches are short and spreading, acute at the tips, 

 and bearing singly the elliptical conidia, which are comparatively small 

 (22-26 x 16-30 ft) and hyaline. 



Within the substance of the petioles and stem the mycelium produces 

 the usual resting spores, which have a yellowish and afterwards a bright 

 brown and rather thick integument (30 x 33 ft). These bodies provide 

 for the rejuvenescence of the parasite in the spring by remaining at rest 

 through the winter. The production and development of these resting 

 spores have already been described in the introduction (ante, p. 2). 



The distribution of this parasite is narrow, only Germany and Belgium 

 having been recorded in addition to Great Britain. 



It has never been sufficiently prevalent or destructive to have been 

 experimented on with fungicides. 



Sacc. Syll. vii. 860 ; Card. Chron. May 1, 1886, with fig. ; Cooke 

 M.F. 237 ; Cooke Hdbk. No. 1786. 



Cyclamen Leaf-spot. 



Two kinds of leaf-spot have been described on the leaves of Cyclamen, 

 but neither of them has as yet been decidedly recognised in this country. 



The French leaf-spot, Phyllosticta Cyclaminis, is manifested by some- 

 what circular brown spots over which the minute perithecia are scattered, 

 and the sporules are small, narrowly elliptical (6-8 x 2 ft), rounded at the 

 ends, and colourless (Bull. Soc. Myc. de France, 1893, t. xiv., f. 4). 



The other species, which we may call the " Concentric Cyclamen 

 Spot," forms rather large and irregular smoky spots, with a rufous 

 margin, the surface being concentrically lined (Septoria Cyclaminis). It 

 was first described in the " Flora of Algeria." The sporules are long and 

 threadlike (25-30 x 1 ft), divided by three transverse septa. This species 

 has occurred in Italy as well as Algeria. 



So far as we are aware, these are the only fungus parasites which 

 have been described as troubling the Cyclamen. 



Auricula Brown Mould. 



Heterosporium Auricula (Cooke), PI. IV. fig. 71. 



About the year 1888 this parasite was first brought to our notice, 

 flourishing upon living leaves of Auricula, and then threatening to 



