Vol. VIII. No. 191. 



THE AGRICULTURAL NEWS. 



267 



FUNGUS NOTES. 



The following article is in continuation of a short 

 series giving an account of the principal points of 

 interest in the life-history of the fungi, and indicating 

 their connexion with practical agriculture. The first 

 of these appears in the last number of the Agricultural 

 liews, p. 251. 



PAliT II. 

 The JIycelium. 



The vegetative portion of a fungu.s is made up of long, 

 narrow tubes or hyphae, which may or may not be divided 

 up by cross walls. The tubes branch frequently, and often 

 join together, spreading in all directions throughout the 

 substance on which the fungus lives. The hyphae may be 

 either coloured or colourless, and frequently contain large 

 oil-drops. Some, of which ^[a)■a■*lnins is an example, are 

 encrusted with crystals of calcium oxalate. 



Unlike most other plants, the fungi cannot obtain their 

 carbon from the carbon dioxide in the air, since they have 

 none of the green colouring matter which is necessary for 

 this. Consequently, they have to make use of food sub- 

 stances which already contain a large amount of carbon, 

 prepared by other plants, or by animals. These plants or 

 animals on which they live may be either living or dead. 

 When the food substance is dead the fungus is said to be 

 a saprophyte ; but when it obtains its nourishment from 

 a living host, the fungus is called a parasite. Saprophytic 

 fungi are very numerous, and usually quite harmless. To 

 this class belong the moulds found <m damp bread, jam, 

 damp leather, ripe fruit, and many other substances. Other 

 saprophytes live on decaying tree stumps, dead leaves, and 

 all kinds of decaying refuse ; examples are the large toadstools 

 often seen on tree stumps. 



Parasitic fungi live on plants and animals. If the fungus 

 grows very rapidly it takes up too much food from the host, 

 ■which consequently dies, and in many cases the fungus can 

 continue to live on the dead host as a saprophyte. These 

 fungi, more especially such as live on plants, are often 

 verj- destructive, and cause planters and farmers much trouble 

 and loss of money ; but some, chiefly those that live on 

 in.sects, are distinctly useful. For instance, one form of 

 fungus will kill caterpillars, another house-tlie.s, while several 

 species are known which destroy the white Ay and the various 

 forms of scale insects found so frequently in the tropics. 



Some fungi are only very weakly parasitic, as for 

 example, that causing root disease of the sugkr-cane, Marax- 

 7Jiiiis sacchari. It lives mostly on the dead' cane leaves or 

 trash, and on similar substances in the .soil ; but when the 

 host plant is somewhat weakened by drought or the attacks 

 of insects, the fungus can obtain a hold as a parasite on the 

 young roots which the plant puts out, and thus the plant 

 .sufteis more and more from want of moisture, and eventually 

 dies. Others are capable of living on many host plants, 

 either on the leaves, stem, roots or flowers. In the case of 

 the root they usually enter those which are young, from the 

 ground, and spread by means of their mycelium, or vegeta- 

 tive part into the older roots : in some cases eventually 

 attacking the stem also. Fungi that attack the stem onlj', 

 usually do so by means of wounds in the bark or rind, where 

 there is a surface of dead cells on which they can begin to 

 grow. Fungi may enter leaves either through their breath- 

 ing pores (or stoniafa), or directly by briring through the skin, 

 or epidermis, as it is usually called. In order to be able to 

 bore through a cell wall the fungus is believed to secrete an 

 enzyme from the tip of the hypha in contact with the wall, 



and on entering the cell it may secrete other enzymes which 

 kill the cell, and enable the fungusjto feed on the remains. 

 In opposition to this, the cell also secretes other substances 

 which may destroy the hyphae of the fungus. Large plants 

 have also another method of repelling fungi ; that is by 

 cutting oft' the water-supply completely from a diseased 

 portion by forming a ring of cork tissue inside it and so kill- 

 ing the fungus. In either case, if the host plant is in good 

 health it may win, if not and the fungus has a good start it 

 will lose, and be possibly completely killed. Thus all 

 methods of cultivation, manuring and drainage which 

 strengthen the plant, help it considerably to overcome its 

 enemy. Want of attention, on the other hand, will frequently 

 weaken the plant and materially assist the attack of the 

 fungus. 



Many fungi, notably the rusts of grasses, spend one part 

 of their life on one host plant, and another jjart on a different 

 host. If either of the hosts occurs in the neighbourhood of 

 the other, the fungus can spread during the year from one to 

 the other, and vice versa, and the presence of one carrying 

 disease will usually mean that the other will become infected. 



Some fungi can only attack one particular form of host 

 plant, and if this host is not grown for .some time the 

 fungus dies out. In the case of such fungi, the degree of 

 parasitism is very advanced. It is thought probable that 

 this limited selection is due to the presence in the host of 

 some particular substance which attracts the germ tube of 

 the fungus when it first grows out from the spore ; the 

 fungus is unable to attack other allied species or even varie- 

 ties owing to the absence of this chemical substance. In 

 other cases, the immune species may possess .some substance 

 which repels the hyphae, while tho.se subject to attack do not 

 to any u.seful extent. 



Species which are immune, through either of these 

 reasons, to the attacks of any given fungus are of the great- 

 est value to the practical planter. A fair estimate can also 

 be formed from what has been said above of the value and 

 importance of rotation of crop.s, and good cultivation when 

 attempts are being made to combat any given plant disease. 



WEATHER FORECASTS IN THE 

 UNITED STATES. 



The field of daily telegraphic meteorological observations 

 for forecast purposes, which in 1896 was limited to the 

 United States and Canada, has been extended by the Depart- 

 ment to embrace at the present time the whole northern 

 hemisphere. Forecasts which formerly were limited to 

 a period of twenty-four to forty-eight hours in advance are 

 now frequently made from four days to a week in advance. 

 In 1896, forecasts were telegraphed daily at Government 

 expense to 1,896 distribution stations, from which points 

 they were distributed by mail, telephone, railway train 

 service, and railway telegraph .service to .51,694 addresses 

 without expense. On June 30, 1908, the daily forecasts 

 were being telegraphed at riovernment expense to 2,.33-t 

 distributing centres, from which points they were distributed 

 gratuitously to 76,1.5-f addresses by mail, .58,008 by rural 

 delivery, 2,139 by railway telegraph, 852 by railway train, 

 and 3,553,067 by telephone, making a grand total of 

 3,690,220 addresse.s, of record, receiving the daily weather 

 forecasts without expense, except for the initial co.st of 

 telegraphing the information from the forecast district 

 centres. The storm-warning display, stations have been 

 increased from 253 to 321. There lias been an addition of 

 seventy-eight stations where daily meteorological observations 

 are taken and telegraphed. (Annual Report of the United 

 States Departiuent oj Agriculture, li>OS.) 



