摘要:

SUMMARY.1Growth maybe divided conveniently into two well‐marked periods. (a) 1st period, from the seedling stage till the time that the plant regains its initial weight after the loss by respiration,i.e.the time during which a casual observer would say the plant “makes no growth.”(b) 2nd period, succeeding the former, during which the plant is obviously making growth, and which continues till the latter ceases and desiccation sets in.2The length of the first period varies inversely with the mean maximum temperature, as the rate at which assimilation is able to make good the loss by respiration increases directly with rise of temperature, up to a certain limit.3The possible amount of growth as measured by the dry matter produced depends directly upon the bright sunshine and temperature when the food supply is adequate, but when the latter is limited the total growth is much less owing to the lack of material for building up the tissues. Beyond a certain limit, however, the beneficial factors of heat and bright sunshine become harmful and result in the premature death of the plant.4During the first period the rate of growth as shown by the efficiency index was associated with relatively warm days and nights, bright sunshine having little significant effect; the light, however, was good throughout for the season of the year. During the second period the rate was associated strongly with sunshine and warm days, but not significantly with the night temperatures, which did not fall below 32° F.5During the greater part of the year the maximum rate of growth (highest efficiency index) is reached early in life, very soon after the second period begins. Under favourable environmental conditions a high rate of increase is then maintained for several weeks, but in less favourable circumstances the efficiency index rapidly falls. In winter, when temperatures rule low and there is little bright sunshine, the maximum rate of growth is not reached till several weeks after the beginning of the second period, and even then the efficiency index is not very great.6Plants with a restricted food supply make less total growth than those with abundant food. The falling off in the amount of dry matter produced does not seem to be gradual but is marked by definite periods of which the incidence varies at different seasons.7Broadly speaking the response of plants to the environmental conditions is similar whether the food supply is abundant or restricted, though the mean rate of growth is lower when food is scarce. During the first period the excess of food has no significant effect upon the rate of growth, but during the second period the mean differences in the rate of increase in the presence of abundance and of scarcity of food are strongly significant in favour of the well supplied plants.8During the early weeks, corresponding approximately to the first period of growth, the shoot/root ratio falls, owing to the steady increase in root weight which is associated at first with a decrease and later with an increase in shoot weight. During the second period of active growth the shoot increases in weight far more rapidly than the root, and thus the shoot/root ratio rises steadily. Increase in shoot growth is closely associated with rise in temperature, though the lowest mean maximum attained in the experiments did not cause a cessation of growth. Root growth is much affected by low mean maximum temperatures and practically ceased, under the experimental conditions, when they were consistently below 60° F. Rise in maximum temperature had much less beneficial action upon the roots than upon the shoots.9In early stages of growth the amount of nitrate absorbed by the plant is relatively large in comparison with the dry matter produced, but later on more dry matter is formed in proportion to the same amount of nitrate, owing to the accumulation of the products of assimilation.In conclusion I wish to express my indebtedness to Mr R. A. Fisher, who has examined the figures and has furnished me with the statistical information embodied in this paper.In each case the efficiency indices are percent

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1920.tb06470.x

出版商:Blackwell Publishing Ltd    

年代:1920

数据来源: WILEY

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1920.tb06471.x

出版商:Blackwell Publishing Ltd    

年代:1920

数据来源: WILEY

摘要:

SUMMARY.Glœosporium piperatumE. and E. andColletotrichum nigrumE. and Hals. are not known to be destructive to chillies in India but they cause much loss of fruit in Burma.These fungi are considered to be identical and to be the conidial forms ofGlomerella cingulata(Stoneman) Spauld. and v. Sch., which is shown to be synonymous withGnomoniopsis(Glomerella)piperataStoneman, the ascogenous stage ofG. piperatumE. and E., according to Miss Stoneman.The perithecia‐producing faculty does not depend on the nutrient medium on which the fungus is grown but depends on the race or strain.This faculty is not a fixed hereditary character but is lost by cultivating successive generations on the same medium at room temperature.There is a great deal of variation in the size and hairiness of the neck of the perithecium and in the size and shape of asci, and therefore cultural characteristics cannot be much relied upon for determining the species.The perithecia are aparaphysate.The ascospores are hyaline, unicellular and slightly curved, but in old perithecia they are found to be septate and their walls coloured brown.In cultures the presence of setae is not a constant character.In cultures of the perithecial strain there are very often sudden variations in the characters of the growth of the fungus.It is doubtful if inoculation experiments are of much value in establishing the relationship of theGlomerellaon chillies with the other species of this genus or in finding its range of hosts, as the success of inoculation depends on several factors all of which may not be controllable.Inoculations on chillies,Carica papaya, and other plants have been described.A new disease ofCarica papayais described. It is caused by the conidial forms of aGlomerella, which is identical with that on chillies in both morphological and cultural characteristics.The disease is found on flowers, young fruits and fruit stalks. Diseased flower‐buds do not open but fall off. If the infection takes place when the flower whorls have opened they turn brown and wither.The most critical period when the fruits get infected is when they are newly set. Older fruits also at times get diseased.Newly set and young fruits get the infection through their stigmas or through the scars of the floral leaves or through punctures on the skin.The infection is marked by the presence of a circular saucer‐shaped depression in the skin.Diseased fruits become mummified, hard and woody.The study of the conidial forms of theGlomerellaonCarica papayaalso shows thatGlmosporiumandColletotrichumare one and the same

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1920.tb06472.x

出版商:Blackwell Publishing Ltd    

年代:1920

数据来源: WILEY

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1920.tb06473.x

出版商:Blackwell Publishing Ltd    

年代:1920

数据来源: WILEY

摘要:

SUMMARY.1Several forms ofH. Lupuluswith yellowish‐green (“golden”) leaves exist. One form (T) has proved persistently immune to mildew both in the greenhouse and in the open. A second form (9) has proved slightly susceptible when grown in the greenhouse. A third form (3) is susceptible in the greenhouse and in the open. This ♂ form appears to be the one found originally in Germany and described under the name ofH. Lupulus aureus.No account of the origin of any ♀“Golden hop” hag been found in horticultural literature.2Certain seedlings raised from the immune ♀“Golden hop” (the ♂ parent being unknown) possess green leaves and are immune to mildew when grown in the greenhouse.3Different seedlings of the wild hop (H. Lupulus) have distinctive physiological or “constitutional” characters, which are constant under the same environment. These characters confer immunity or susceptibility, or intermediate grades of susceptibility, on the respective seedlings. The immunity is retained by the plant after four years' residence in the manured soil of the hop‐garden.4Certain seedlings of the wild hop which show persistent immunity when grown in the greenhouse show some degree of susceptibility when grown in the open. The susceptibility shown is usually very slight. There is some evidence that this breaking down of immunity is due to the effect of certain climatic conditions.5In the great majority of cases, the greenhouse conditions do not have the effect of making seedlings of the wild hop immune to mildew. In the case of some seedlings extreme susceptibility is shown under greenhouse conditions.6The phenomenon of semi‐immunity is shown by certain seedlings of various origins.7A form (8) ofH. americanusNutt., obtained from the United States, has proved immune to mildew under greenhouse conditions. Under the same conditions several American cultivated

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1920.tb06474.x

出版商:Blackwell Publishing Ltd    

年代:1920

数据来源: WILEY

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1920.tb06475.x

出版商:Blackwell Publishing Ltd    

年代:1920

数据来源: WILEY

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1920.tb06476.x

出版商:Blackwell Publishing Ltd    

年代:1920

数据来源: WILEY

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1920.tb06477.x

出版商:Blackwell Publishing Ltd    

年代:1920

数据来源: WILEY

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1920.tb06478.x

出版商:Blackwell Publishing Ltd    

年代:1920

数据来源: WILEY

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1920.tb06479.x

出版商:Blackwell Publishing Ltd    

年代:1920

数据来源: WILEY