884 



THE TROPICAL AGRICULTURIST. 



[June 2, 1884. 



incredulity. In plate 54 of the present publication, how- 

 ever, we find a fruit represented which might be taken for 

 that of a Cucumber ; it is, however, entered as Oucumis 

 Melo var. utilissimus, and concerning which we extract the 

 following notes: — ^*'Thi8 is another of the extreme forms 

 or varieties of the Melon, differing in the shape of the 

 fruit and the uses to which it is applied. The fruit varies 

 from short-oval or cylindrical to elongate, and is either 

 straight or curved, like some varieties of Cucumber. Some 

 specimens grown this year in the Saharunpur Garden meas- 

 ured over ;i yard in length. They also vary in colour from 

 dark green to nearly white, usually changing to a bright 

 orange colour when ripe. The seeds, like those of * Phunt,' 

 are rather smaller and more slender than true Melon seeds. 



Roxburg, Flora Jndica^ I.e., makes the following remarks 

 on this plant: — 'This appears to me to be by far the most 

 useful species of Cucumis that I know. "When little more 

 than one-half grown they are oblong and a little downy; 

 in this state they are pickled. "Wlien ripe they are about 

 as large as an ostrich's egg, smooth and yellow. When 

 cut they have much the tiavour of the Melon, and will 

 keep good for several months if carefully gathered with- 

 out being bruised and hung uji ; they are also in this stage 

 eaten raw, and much used in curries by the natives. The 

 seeds, like those of other cucurbitaceous fruits, contain 

 much farinaceous matter blended with a large portion of 

 mild oil. The natives dry and grind them into a meal, 

 which they employ as an article of diet ; they also express 

 a mild oil from them, which they use in food and to burn 

 in their lamps. Experience as well as analogy prove these 

 seetls to be highly noiurishing, and well deserving of a more 

 exten.sive culture than is bestowed on them at present.' " 



It appears from these plates that cucumbers in India 

 have sometimes egg-shaped fruits, while some Melons have 

 long cylindrical fruits of the shape we at home associate 

 with the Cucumber. It will be remembered that M. Naudin 

 conclusively proved the specific identity of these forms by 

 the experimental culture of every obtainable variety — a 

 striking instance of the valuable resi^dts to be got from 

 botanic gardens. "We strongly commend the perusal of 

 this work to the notice of those of our colonists whose 

 lini'S may be cast under climatal conditions suitable for the 

 growth of these Cucurbits, which are grown in certain 

 pa rts of India on a scale which will excite the surprise of 

 the reader. — Gardeners' Chronicle. 



FUNGI ON PLANTS. 



Sir J. B. Lawes, of Kothamsted, in the last number of 

 the journal of the Royal Agricultural Society of England, 

 says : — " I consider that plants are Uable to be attacked by 

 fungi, parasites, &c., in proportion as the soil is deficient in 

 available mineral food. ... It is quite possible that 

 when the climate favors mildew it will prevail more or less, 

 but that the extent to which it will prevail will greatly de- 

 pend upon the relation between the mineral aud organic 

 matter in the soil, and I should be disposed to say that the 

 greater the amount of available mineral matter (potash, 

 lime, silica, phosphate) at the disposal of the plant, the 

 greater would be its power of resistance. . . . "We learn 

 that in bad seasons the best crops are attacked with mildew, 

 if that is the prevaling disease ; but the power of resistance 

 to disease is greatly affected by the condition of the soil. 

 . . . Plants are very much like ourselves — their power 

 to escape disease, aud to struggle against it when attacked, 

 depend very much upon their state of health." Dr. Yoelck- 

 er says : — "I believe the soil has a great deal to do with mil- 

 dew. . . . An excess of available nitrogenous food (be 

 it nitrate of soda, ammonia salts, or organic matters which 

 are readily decomposed in the soil), appears to have a de- 

 cided t-endency to cause mildew in wheat." The report on 

 wheat mildew by Mr. Little, from which the above extracts 

 are taken, concludes thus: — "It would appear that seasons 

 are the chief cause of mildew, aud that sudden changes of 

 temperature and rain, accompanied with close still weather, 

 are favorable to the spread of the disease. That low-lying 

 rich soils are most subject to attack. That high farming 

 and too generous manuring, particularly with nitrogenous 

 manures, promote mildew. That early sowiug is desirable. 

 Th:ii while no description of wheat is proof againstdisea.se, 

 red wheats are generally less injured by it than white wheats. 

 . . "SN'hile I have been most anxious to prove that at- 



mospheric conditions are not the sole governing cause of 

 mildew, I must not be supposed to deny for one moment that 

 a condition of humidity and saturation of the air is required 

 to develop the disease. Again, I think that the exact in- 

 fluence of particular chemical constituents on the tissues of 

 the plant is deserving of further inquiry." Mr. Little 

 also says: — "AVheat mildew is caused by a parasitic fungus, 

 known as Puccinia graminia, which attacks both oats and 

 barley, as well as many of the natural grasses. This parasite 

 lives within the cellular tissue of the plant, sapping its vitals, 

 aud converting to its own use the sap which should nourish 

 and mature the graiu. The presence of this fungus iu the 

 infected host plant is evidenced only byits fruit, or reproduct- 

 ive organs, which burst through the cuticle and appear in 

 red or black patches on the leaves, straw, or chaff. The life 

 history of this fungus is remarkable, as, according to the 

 investigations of Mr. C. B. Plowright, M.R.C.S., a well 

 knowm authority on British fungi, it has no less than five 

 kinds of reproductive forms — (Ecidium, Spermogonia, Uredo, 

 Puccinia and Promycelium, Of these fi.ve forms three only 

 — (Ecidium, Uredo and Puccinia — come under the notice of 

 the ordinary observer. . . . Starting then from this 

 point — that is, ^vith the blackened straw of the previous 

 year — we find that in the spring the Teleuto spores are 

 quickened into life, and from them are produced another 

 kind of spores (Promycelium spores), which are said to be 

 unable to retain life and bear fruit unless they can meet with 

 a barberry-tree. Having settled upon a leaf of one of these 

 shrubs, the spore bores iuto the interior, and there develops 

 in Mycelium, which, in the com*se of about eight days, pro- 

 duces rusty patches on both the upper and under sides of 

 the barberry leaf. From these spots of rust, two different 

 kinds of spores are shed — CEcidium spores from the under, 

 and Spermogonia from the upper side of the leaf. It 

 is supposed by Mr. Plo\vright that they are of differ- 

 ent sexep, the smaller spores, or Spermogonia, playing the 

 part of tlie male. The CEcidium spores (perhaps fertilised 

 by the Spermogonia) are distributed in the air in incalculable 

 numbers, aud those which fall on plants adapted to fulfil 

 the office of host plants germinate under favorable atmo- 

 spheric conditions — that is to say iu damp weather — and throw 

 out a germ tube, which enters the host plants through one 

 of its stomata or breathing pores. Having effected an en- 

 trance, MyceHum is again developed in the tissue of the 

 plant (wheat or grass), and the fungus has now obtained 

 possession of a home in which it can complete its life cycle. 

 In the course of ten or twelve days Uredo spores are pro- 

 duced on the outside of the leaf. These are distributed and 

 germinate and reproduce their kind. The reproduction of 

 Uredo is repeated generation after generation until the host 

 plant approaches maturity, when the Mycelium throws out 

 Teleuto spores aud the life cycle is completed." — Leader. 



CANKER IN APPLE TREES. 



There are probably several diseased conditions of Apple 

 trees known as canker. During the past two or three 

 months I have "been lookmg into this disease somewhat 

 attentively, and I have come to the conclusion that the 

 commonest and most serious form is due, as was pointed 

 out by Goethe, to a sphceriaceous fungus, Nectria ditissima 

 (Tul.).* The various members of Sph;eriacei occur, as a 

 rule, upon dead wood — not upon the living tissues of plants. 

 There are, however, many important exceptions — such, for 

 example, as the Yalsa parmularia, described many years 

 ago by Mr. Berkeley, upon living Oak twigs. More im- 

 portant, from an economic point of view, is the Sph.i^ria 

 morbosa of Schweiuitz, the cause of black knot in Cherry 

 aud Plum trees in the United States: closely allied to 

 which is Gibbera vaccinii upon living branches of Vacci- 

 nium "Vitis-Ida^a in our own country. The Dothideacea?, 

 too, occur, manj' of them, upon living leaves and branches, 

 as the genus Phyllachora for example. Although there is 

 nothing impossible in the notion that a Nectria may be 



* Nectria ditissima. Tub, Carp., iii., p. 73, t. 13, f. 1—4 

 (=N. coccinea of many authors). — Peritlu-cia widely scat- 

 tered or densely gregarious, globose-obtuse then pajiillate, 

 naked blood red asci cylindrico-clavate, 82 k 8 mk.; sporidia 

 ovate-oblong, uniseptate. 14-^6—8 mk., hyaline. l\>ni(iia 

 tidiercidaria crassostipitatay Fuckel, Hi/mh. J/t/roL, p. 180. 

 Conidia ovate-oblong, continuoas, 6 — 8m3 — 4 mk. 



