346 THE FLORIST. 
the disease. Believing that fungi of divers kinds exist'in the air, and 
wait for settlement and adaptation of weather and plants for establish- 
ment and growth, and believing ‘that’ Rose mildew’ is’ an’ external 
fungus, I will, on. this supposition (for I ‘am’ not sure), turn from 
internal to external! fungis' Such are the mildews that affect Onions, 
Peas, Cabbages,' the leaves and stems of’ Roses,’ and also ‘living ‘and 
dead vegetables, or woody substances. © For instance, cut a ‘Lemon in 
two, and, in’ moist’ ‘weather suitable to' fungus; in ‘less than forty-eight 
hours a rooted and’ growing’ fungus’ will, be established from wothout ; 
for I cannot think’ that‘it is mere putrefaction; or disease’ produced 
through the'cireulation. Again, throw stable mauure into a heap, and 
let it lie, and in due time'fungi will pitch upon it; take root, and come 
up in the form' of Toadstools.'' I believe that the case‘is the ‘same with 
the fungus of mildew on Roses. ‘The spores or sporules pitch upon the 
leaves and adhere to the stickiest, and when’ the weather is suitable 
(Mushroom weather), they root into the tender skins of the youngest 
leaves, and feed’ upon ‘the parenchyma, and stop the respiration of the 
plant, and destroy the léaves,*which are the lungs ‘of the’ plant. Rose 
mildew, if viewed through ‘a powerftl lens; will be seen to be monilious, 
or, to speak plain, jomted like'a necklace; and°I “suppose that it is the 
same form of fungus as that which'is called Acrosporium monilioides. I 
have, however, viewed some leaves of Boula de’ Nanteuil, the only Rose- 
tree that now has mildew, and my microscope represented the’ mildew 
as an infinite number of Mushrooms, surrounded by their spores. ‘Till ~ 
this “external” theory is controverted ; “or; till I have been enabled by 
more powerful glasses—for which T' have sent to London—to detect my 
fallacy, I shall’ believe it ‘to be true.’ Inthe meantime, I hope that’ no 
false delicacy will deter any one more ‘versed in natural philosophy than 
Tam from correcting any erroneous statements that I may have fallen 
into. I, for'one, shall’ be truly ‘¢lad to be corrected, if in error, and to 
be advised. | 
Turning from theory'to undoubted facts, I will observe that some 
Rose trees are more easily and sorely affected with this fungus than 
others, taking more or less injury according to the earliness or lateness 
of the season of its attack. Among summer Roses, Ohl and Madeline 
are most liable to it. Among autumnals the Géant (taken the 8th of 
May) and its race generally are very liable to it. This summer, how- 
ever, mildew has attacked all kinds of Roses, save those on their own 
roots. Manetti Roses, from their extreme succulence, are most fayour- 
able to its development; ‘yet the following Manetti’ Rose trees, viz., 
Acidalie, Mont Carmel, and Duchess of Norfolk have escaped alto- 
gether.’ While the General Jacqueminot on alien stocks have been 
much ‘affected, a fine tree of it, on its own roots, on the same bed with 
afflicted ones, has retained the cleatiest,; most vigorous, and dense green 
foliage. Of Roses on alien stocks, the lawn hole ones were the least 
affected, and the river side ones, where growth is quicker, were the 
most affected. Even summer Roses, which usually are freest from leaf 
blights, have been much and generally affected. I suppose that’ the 
development of the fungus, which adheres to all sticky leaves alike, 
depends upon the power of the spores to penetrate and root into the 
