126 



THE GARDENER'S ASSISTANT. 



Disease. — After the diseased leavesand flowers 

 have fallen the Rose-tree is perfectly free from 

 disease, and would remain so unless a fresh 

 inoculation of the leaves occurred the following 

 season. This would depend entirely on the 

 presence of winter fruit of the fungus in the 

 vicinity of the Rose-tree, and such must neces- 

 sarily have been produced the previous season; 

 hence it is of primary importance in every 

 instance where a disease has previously existed, 

 that all parts of diseased plants, leaves, fruit, 

 &c, should be collected and burned — not thrown 

 on a rubbish-heap — otherwise the winter fruit 

 present on such will in all probability give 

 origin to the disease afresh the next season. 

 Diseased plants should not simply be placed in 

 some out-of-the-way place and forgotten, and 

 thus allow the spores to diffuse, but should be 

 destroyed; or, if valuable, all diseased parts 

 should be removed and the plant sprayed with 

 a fungicide. Success in keeping plants free from 

 fungous diseases depends much more in carry- 

 ing into effect a few simple rules, as stated 

 above, than in possessing a profound knowledge 

 of fungi, and perhaps the most important point 

 is that of never neglecting to check a disease 

 on its first appearance. Half-measures always 

 end in disaster. 



The above remarks do not apply to Rose Mil- 

 dew only, but are of universal application. 



A second type of fungi included under the 

 popular name of "mould", and known botani- 

 cally as Sclerotinia, proves very destructive to 

 Lilies, Crocuses, Snowdrops, and bulbous plants 

 in general; while another section of the same 

 group destroys Cucumbers, Melons, Scarlet- 

 runners, Potatoes, tV'C. The members of this 

 group possess three distinct methods of repro- 

 duction. There is the usual summer form of 

 fruit, which appears under the form of a delicate 

 gray mould, forming small, minute velvety 

 specks on the leaves and flower-buds of Lilies, 

 on the leaves and flower-spathes of Snowdrops, 

 or commences near the ground and spreads up 

 the stems of Potatoes, Chrysanthemums, Melons, 

 and numerous other plants. The mould or 

 summer fruit as usual enables the fungus to 

 spread quickly, the rapidly-formed spores being 

 blown by wind from one plant to another, 

 which in turn become diseased, and form a 

 new centre from which spores are liberated. 

 During the summer the mycelium of the fungus 

 spreads rapidly in the tissues of the diseased 

 plant, in the case of bulbous plants passing into 

 the bulb or permanent portion of the plant, 

 where it forms into small compact lumps, vary- 



ing in size from a pin's head to that of a Vetch 



seed, depending on the particular kind of fungus 



causing the disease. These lumps are at first 



| white, eventually becoming black outside, and 



I are called Sclerotia, and may be found embedded 



j in the outer scales of the bulb, and also in the 



substance of the stem just above-ground. In 



Fig:. 16 s. — Brown Vine Mildew (Sclerotinia fuckeliana). 



1. Summer fruit on portion of a Vine leaf (reduced in size). 2. Summer 

 fruit (natural size). 3. Portion of summer fruit (magnified 300). 4. Win. 

 ter fruit springing from a small black sclerotium (natural size). 5. Mode 

 of spore formation in winter fruit (magnified 200). (Journal Royal Hor- 

 ticultural Hocitty.) 



Potatoes, Cucumbers, &c, the sclerotia are 

 formed in the pith of the dying stems, where they 

 are often very numerous, and readily seen owing 

 to their black colour when mature. Sclerotia 

 correspond to winter fruit in function; that is, 

 they require a period of rest before they can 

 commence renewed growth. In the case of in- 

 fested bulbs, the sclerotia rest during winter 

 along with the bulb, and when the latter com- 

 mences growth in the spring, the sclerotia either 

 at once form mycelium, which passes into, and 

 grows along w r ith the leaves and flowers, coming 

 to the surface of the plant to form spores in the 

 air as the season advances, or the sclerotia at 

 first give origin to a very different form of fruit, 

 resembling in shape a miniature wine-glass, 

 supported on a long, slender stalk, which ap- 

 pears to spring from the ground. This form of 

 fruit produces spores which are liberated at 

 maturity, and those that happen to alight on 

 damp leaves germinate, enter the tissues of the 

 plant, and soon give origin to the summer form 

 of fruit. 



When bulbous plants are attacked by disease 

 the bulbs should be examined, and those in- 

 fested with sclerotia should be destroyed, as 



