118 ON THE WHITE RUST OF CABBAGES. 



dition to show that it had no near affinity ^vith Uredo, tliat it 

 had still less with the parasitic moulds, that at any rate it was 

 produced beneath the surface of the leaf, and that the spores 

 oozed out by reason of the contraction of the substance of the leaf 

 upon the pulpy mass stored up beneath the cuticle. There was 

 indeed some difficulty about the genus, but little as to its true 

 affinities. In the spring of 1850 a single plant of cauli- 

 flower attracted my attention from its leprous aspect, which 

 seemed somewhat different from that exhibited by otlier plants 

 attacked by the common white rust (Ci/stopus canclidtis). On 

 examination it was, to my great delight, clear that I had at last 

 discovered the doubtful plant of Greville. The summer proved 

 most unpropitious to the growth of cauliflowers, few coming to 

 perfection till late in the year, whatever the variety might be. 

 Mine consisted of those distributed by the Horticultural So- 

 ciety, with the addition of the Walcheren, and neither my own 

 garden nor those of my neighbours, who had merely the old 

 variety commonly grown, exhibited a really good specimen ; and 

 the complaint probably might have been made very generally, as 

 an inspection of the specimens exposed for sale in Covent Garden 

 during the summer, on more than one occasion, showed that at 

 least for part of the season they were neither plentiful nor well 

 formed. At any rate the crop was most miserable here, and at 

 the end of June and the beginning of July, in a large garden 

 where multitudes are grown for the supply of the neighbouring 

 markets, almost every plant, amongst which there was scarcely 

 one wliich had not run, was white with the same interesting 

 fungus which I had observed earlier in the year at home. 



How far the condition of the crop might be due to any pecu- 

 liarity of the season, or to the presence of the fungus, whose 

 growth was favoured by the state of the atmosphere, it is impos- 

 sible to say, though both in the case of the Cystojms and the 

 fungus under consideration, I have observed a tendency in the 

 plants infested to produce a multitude of green bracts amongst 

 the flowers, greatly impairing the beauty, and consequently the 

 market value, of the produce, even where tolerable heads are 

 formed. 



The parasite forms, both upon the upper and under surface of 

 the leaf, roundish often confluent patches, varying greatly in 

 size, consisting of little white specks disposed more or less con- 

 centrically, those of the centre frequently becoming yellow, and 

 at length fading away, in consequence of tiie partial decompo- 

 sition of the leaf which they have affected, while the outer 

 pustules spread from the circumference to the part yet remaining 

 healthy. Occasionally they extend to the midrib, which is then 

 rapidly destroyed. On close examination it is found that the 

 fungus, each speck forming a distinct individual, is produced 



