October 4, 1877. ] 



JOURNAL OP HORTICULTURE AND COTTAGE GARDENER. 



263 



WEEKLY CALENDAR. 



Day Day 



of I of 

 Month Week. 



OCTOBER 1—10, 1S77. 



4 

 5 

 6 

 7 

 8 

 9 

 10 



Th 



F 



S 



Son 



M 



Tu 



W 



WeEtminstU' Aquarium Potato Show. 

 19 Sunday afteb Trinity. 



T. A. Knight bom, 1758. Oxford Hkhielmas Term 



[ commences. 



Average 



Temperature near 



London. 



Dav. 

 63-7 

 60.5 

 61.8 

 637 

 61.7 

 60.7 

 61.6 



Night. 



42.4 

 40.3 

 43.2 

 43.1 

 42.0 

 42.4 

 43.3 



Mean 

 53.1 

 50.4 

 52.5 

 536 

 51.8 

 51.5 

 52.4 



Sun 

 Rises. 



Snn 

 Sets. 



6 16 

 6 18 



Moon 

 Rises. 



5 31 



7 1 



8 31 



9 59 

 11 23 



Moon 

 Sets. 



h. m. 



2 25 



4 39 



4 53 



5 8 

 5 26 

 5 50 



Age. 



before 

 Sun. 



Days. 

 27 

 28 

 O 

 1 

 2 



11 22 



11 40 



11 57 



12 15 

 12 31 



12 47 



13 S 



Day 



of 



Year. 



277 

 278 

 279 

 £80 



2ei 



2S2 

 283 



From observations taken near London during forty-three years, the average day temperature of the week is 61.9- ; and its night temperature 

 42.4^. 



GENERALISMS ON MILDEW. 



CORRESPONDENT on page 191 of our 

 Journal bewails the uncontrollable ravages 

 of rnildew among bis Roses, and, wbile ask- 

 ing for further information, gave a number 

 of so-called preventives and cures, which on 

 being put to the test proved in each case, 

 if not complete failures, yet most unsatis- 

 factory in the general result. 



The writer of the following lines, as a 

 sufferer year after year from the same wide- 

 spread cause, gladly hailed the appearance of a paragraph 

 in the Journal headed, " Rose Difficulty." At last, he 

 thought, I shall obtain some practical information — some 

 probable solution of this mysterious visitation, even if a 

 perfect cure were not to be expected ; but, alas ! no. 

 The " City Clerk," an unmistakeably zealous but in- 

 experienced brother horticulturist, merely states his 

 grievance, and then puts a varied string of questions, 

 which doubtless some other correspondents will answer 

 seriatim. 



Perhaps, as no one has taken up as yet the subject, the 

 following generalisms as to the nature, object, prevention, 

 and cure of mildew may not be wholly useless. Few 

 horticulturists of the present day require to be reminded 

 that mildew (called after two Saxon words meaning meal 

 dew) is in its true character a plant, a vegetable parasite ; 

 and although at the beginning of the present century its 

 ravages were attributed to blight, honeydew, or diseases in 

 the plant itself — to any source rather than the real one — 

 attacks of myriads of destructive fungi, yet its fearful 

 effects as causes of famine or pestilence both biblical and 

 classical literature in the time of the Jews and Romans, 

 and nearer our own time in the Middle Ages, conclusively 

 hand down to us. 



There are three different kinds of mildew — 1, affecting 

 superficially the leaf ; 2, the interior of the stem or leaf ; 

 and 3, the root. It is with the first of these kinds that our 

 gardens are mostly attacked ; it may be added en passant 

 that, as a rule, though not always, each species of plant 

 has one special species of fungus at least peculiar to it. 



It is of melancholy interest to notice here that of the 

 four sub-orders of the great natural order Rosaces, three 

 (one is entirely tropical) are specially liable to attacks of 

 fungus or mildew in some form or the other. No. 2 sub- 

 order, Chrysobalaneas, gives us through the Almond tree 

 our Peach and Nectarine, both fruit trees, especially the 

 former, in many situations annual victims to this pest. 

 No. 3 sub-order, Roseau, gives us (nursed originally in the 

 cradle of the Dog Rose, through Rosa Gallica or Provens 

 Rose and our old Centifolia or Cabbage Rose), the queen 

 of flowers, alas! so often disfigured and injured by the 

 same fell influence. No. 4 sub-order, Porneae, gives us 

 among edible fruits the Apple and Pear, which suffer 

 terribly under periodical visitations from several para- 

 sitical fungi peculiar to them. 



I may mention here, in answer to the "City Clerk's " 

 question as to whether the disease on the back of the 



No. 862.- Vol. XXXIII., New Seeies. 



Laurel leaves, very prevalent now in Surrey, is the same 

 as Rose mildew, that, unusual as I believe the circum- 

 stance to be, most probably it is ; at any rate the same 

 phenomenon was observed last July in Herefordshire 

 by several reliable individuals, where the leading shoots 

 of neighbouring Apple, common Laurel, and White- 

 thorn trees were discovered to be infected with precisely 

 the same parasitical plant or fungus, first appearing 

 as a white, but changing afterwards to a rusty-coloured 

 mildew. 



The appearance of mildew takes the form generally of 

 white or black spots on an uneven patchy surface either 

 as a rusty powder or frosty incrustation, in every case 

 spreading unless checked in an early stage, and by pre- 

 venting respiration crippling the growth of the flower or 

 fruit, and causing the leaves to fall, if not the plant itself 

 to die. 



The usual period for the appearance of this widespread 

 pest (for it is co-extensive with all animal life) is in the 

 autumn, as with all other fungi, and it is far easier to 

 speak of the causes that produce them than of their pre- 

 vention or cure. The rapidity with which they arrive 

 at maturity and the enormous number of seeds they 

 produce is something incredible. One great analytical 

 mycologist (Mr. Worthington Smith) could tell us, so as to 

 allow us to realise some approach to the aggregate num- 

 ber produced, that one Mushroom was sufficient to pro- 

 pagate 250 millions ; while only twenty-four hours is 

 necessary with some fungi to intervene between the first 

 springing of the plant and the ripening of the seed. 



It should be remembered that it is the first kind, or 

 superficial mildew, alluded to here, which, being as seeds 

 communicated when ripe to the air, establish themselves 

 on one plant after the other wherever they touch, destroy- 

 ing the plant with which they come in contact, as has 

 been stated, by preventing respiration. All this is the 

 unanswerable outcome of observation and experience, 

 and as such matters of fact. Would that the prevention 

 and cure of mildew could be as easily and satisfactorily 

 disposed of. 



Dr. Lindley — and his authority carries great weight — 

 considered that as " plants are generally most affected by 

 superficial fungi after a long drought, when the fibres of 

 the roots are unable to imbibe sufficient moisture from 

 the soil, and the plant becomes debilitated and affords 

 an easy prey to the parasite which attacks it," the cure 

 seems to be abundant watering, and assigns as a proof 

 that in Scotland where there are heavy night dews this 

 fungus is unknown. But surely, especially when viewed 

 at such a humid season as the present, the subject is still 

 left open, and many other agencies still to be considered 

 accountable for the production of fungi besides drought. 

 The view which seems to meet more fully the whole 

 circumstances of the phenomena is that changes are 

 undergone, as in the case of the Potato disease, in the 

 cells and vessels of the leaves, say of the Rose, by cultiva- 

 tion (how seldom does one see mildew under any cir- 

 cumstances on the Dog Briar), which render the plant 

 liable to disease : atmospheric influences, such as sudden 



No. 1514.— Vol. LVIII., Old Seeies. 



