54 



JOURNAL OP HORTICULTURE AND COTTAGE GARDENEK. 



[ July 20, 1876. 



through the hundreds of thousands of breathing spores (d d) 

 of the leaf. The common form of the fungus is seen emerg- 

 ing through these breathing pores and producing its fruit at F. 

 This fruit at a certain period of growth exhibits the marks 

 as shown on the cut ; these marks are similar in character to 

 the lines seen on water when it begins to freeze. Later on the 

 fruit or spore bursts into about six, seven, or eight portions, 

 and each portion soon acquires two tails as seen at g. These 

 latter tailed bodies are the zoospores, for, though vegetable in 

 nature, they swim about by their two tails like animals, and 

 often float again into the very Bame breathing pores from which 

 the thread which bore them only shortly before emerged. Dew, 

 mist, or rain supplies the moisture in which they float on the 

 leaves. Now, wherever these zoospores germinate they at 

 once (by poisoning the material of the plant) give the Potato 

 the murrain, and the experiment which proves it has been 

 repeated many times and by different competent observers. 

 As the healthy Potato will always take the murrain from these 

 spores as certainly as a healthy man will take the small-pox 

 when inoculated for that disease, it is reasonably considered 

 by botanists that the Potato fungus will cause the disease. > 



The various dark circular bodies seen in the illustration are 

 the mature resting spores of the Potato-disease fungus as ob- 

 tained by me from the Chiswick Potatoes last year. At first 

 they were carried on threads and were semi-transparent and 

 much smaller in size, and in this latter condition they were 

 illustrated for the Journal of Horticulture last summer. They 

 arose, as is there stated, by a male anther-like body attaching 

 itself to a female stigma-like or pistil-like body. From this 

 contact arose the eggs or resting spores of the Potato fungus. 

 During the months of May and June last most of these resting 

 spores germinated. The first sign of renewed life was the 

 cracking of the outer skins as at h h, just as the skins of some 

 seeds crack prior to germination. An inner bladder was often 

 expelled as at j, and this bladder may be seen still inside the 

 resting spores at k k k k. This bladder in its turn frequently 

 cracked to pieces and set a number of tailed zoospores free 

 exactly similar in character with the zoospores produced at r, 

 and one of which is seen free at o. On being placed upon 

 slices of Potato and upon Potato leaves they at once grew, 

 corroded the cells of the plant, and reproduced the murrain. 

 Other of the resting spores, as shown at l, l, l, l, did not 

 produce zoospores, but instead of these bodies they showed 

 the spawn coiled up worm-like within. When the outer skins 

 of these latter resting spores cracked the spawn unwound as 

 at M, emerged and got free as at n, and exhibiting a joint at o 

 produced the fungus of the Potato disease terminal as at p. 



Now, although these phenomena are described in a very 

 few words, they represent a whole year's harassing, anxious, 

 thankless work. As I did not know whether the resting spares 

 intended to sleep for ten days or ten months, I was under the 

 necessity of constantly watching them. Everyone knows how 

 a batch of apparently healthy seeds may on germination all 

 damp-off and die, and how to avoid this different soils, tempe- 

 ratures, and conditions must be tried by seed-growers. In the 

 Bame way I divided my material, and to avoid any chance of 

 failure got the resting spores to grow under every condition of 

 which I could think. They grew remarkably well under most 

 of my conditions, the best being, probably, expressed juice of 

 Potato leaves upon moist fragments of clean broken flower- 

 pot and in diluted expressed juice of horse dimg upon similar 

 fragments, always kept moist and shaded under darkened bell- 

 glasses. Most of my conclusions (and all the really critical 

 ones) have been confirmed either by the Rev. J. E. Vize, Mr. 

 C. B. Plowright, or Mr. C. E. Broome. A strong attempt was 

 made last year to connect my resting spores with one of the 

 Saprolegnicas (as they are termed) , fungi commonly found upon 

 decaying insects in water, and because I illustrated my spawn 

 threads with joints an equally strong objection was taken to 

 these jointed threads because the insect fungi have threads 

 without joints. But my spawn threads were correctly repre- 

 sented as jointed ; the Potato fungus has jointed threads, and 

 one of the resting spores which germinated displayed three 

 joints. On sending the mounted preparation with the draw- 

 ing to Mr. Berkeley for confirmation he replied, " I found the 

 germinating oospore exactly as you figure it. There can be 

 no doubt about the matter." There is a second fungoid pest 

 of Potatoes named Fusisporium solani. This pest, says Mr. 

 Berkeley, " causes rapid and loathsome decay, especially when 

 in company with the Peronospora." It generally is in company 

 with it, and the two marauders were together last year at 

 Chiswick, and in attempting to bring down the Peronospora I 



shot both birds with one charge. The fruit of the Fusisporium 

 is shown on its thread at Q. The fruit has three joints, and 

 so each fruit commonly produces four new plants ; but during 

 my experiments I have observed that certain fruits instead of 

 germinating at once round themselves off into Bpheres as at 

 e, b. These spherical bodies then go to rest for about two 

 months, when they burst as at s and at ones renew the species, 

 so that under favourable circumstances we get six resting spore 

 generations of Fusisporium and one of Peronospora every 

 season. 



I have maintained the resting spores of both fungi in vigor- 

 ous health — 1, in old decaying Potato leaves kept moist; 2, in 

 Bcrapings of the tuber kept more or less water and damp air ; 

 and 3, in diluted expressed juice of horse dung. I have not 

 the slightest doubt in my own mind that the resting spores of 

 both the above-described pests naturally abound every year in 

 myriads in old moist Potato refuse, especially when it is 

 allowed to remain about ditch sides, damp places, and dung 

 heaps, and from these situations and upon the ground the 

 Potato fungus first grows, and there the disease springB every 

 year. 



Since my observations were printed last year many papers 

 have been published on the same subject, and some botanists 

 have obtained an organism similar in some respects with mine. 

 De Bary's plant may be taken as a general type of all. It is 

 called a species of fungus new to Bcience by De Bary under the 

 name of Pythium vexans, and I have engraved it at t to the 

 same scale as the bodies observed by me. De Bary does not 

 claim his plant to be the same with mine, although a suggestion 

 to this effect has been made elsewhere. De Bary's plant is 

 much smaller than mine, and has continuous threads without 

 joints ; my plant is carried on jointed threads and produces 

 a resting spore which sleeps for ten or eleven months before 

 germination. De Bary's plant has no true resting spore. My 

 plant grows upon and appears to be peculiar to Potatoes, 

 whilst De Bary's only produces fruit or dead insects. 



When the habit of a disease is fully known a cure or palli- 

 ative ought to be forthcoming, unless the disease is incurable. 

 There seems to bo no reason why something should not be 

 done with the Potato disease, especially after what has been 

 done with the disease of the Vine and other plants, but just 

 now any suggestion for remedial treatment muBt be premature. 



When my firBt notes were published I attached very little 

 importance to them', and I had no settled intention at that 

 time of carrying my experiments any further. As my obser- 

 vations were, however, seriously challenged in different quarters 

 I thought it better at extreme inconvenience to myself to 

 watch the bodies discovered by me in the Chiswick Potatoes 

 through an entire year. The result is now before your readers. 

 If no one has seen these bodies before it is simply because 

 they have not looked for them in the right place and in the 

 right material. That the resting spores are produced in 

 millions in decayed Potato material there can be no manner of 

 doubt, and as Mr. Broome has also obtained the same resultB 

 I do not stand alone. 



The work to be taken in hand now is to prevent the forma- 

 tion of the resting spores, or if formed to destroy them. If 

 these bodies are once killed Potatoes will not suffer much from 

 the ordinary spores or the " perennial mycelium " in the tuber 

 pointed out by Mr. Berkeley in 1845.— Woethington G. Smith. 



SYRINGING. 



Had " W. J. B." reserved his opinion until in possession of 

 all the facts, it might have been different to that given at 

 page 466. Your correspondent states, " that even in nature 

 if the rain could reach the under Bides of the foliage of trees 

 it would often be of great benefit ;" but " if we follow nature," 

 writes " W. J. B.," "we find that during showery weather 

 vegetation is freer from insects than during a time of drought." 

 This is clearly not because it "rains upwards," but is effected 

 by the action of the water upon the upper surfaces of the 

 leaves. " W. J. B." instances two Rose trees which he ex- 

 perimented upon by syringing one regularly and not syring- 

 ing the other, and in one case he had " healthy foliage and 

 fine blooms," in the other " thousands of insects " — only what 

 might have been anticipated. His Kose evidence shows neither 

 the necessity, or otherwise the value, of syringing the under 

 side of the leaves. " The water was applied to the under side 

 of the foliage, but it did nothing but good." Decidedly, no 

 injury could follow ; but would not the result have been equal 

 had the other Rose had distributed over its head a like quantity 



