162 



THE AGRICULTURAL NEWS. 



May 28, 1910. 



The subject may be further considered at sonie- 

 Avhat greater length from a different point of view. 

 Since the fungi are unable to obtain their own food- 

 supply from the air, it follows that they must obtain it 

 already manufactured from one or more sources. The 

 only organism that can manufacture its own food-supply 

 from the air is the green plant, so that, clearly, one 

 possible source of food for the fungi is the bodies of 

 such plants, either alive or dead: moreover, since 

 anioials may be legarded as fundamentally depend- 

 ent on green plants for their food-supply, their dead 

 or living bodies also offer a possible source of food to 

 the fungi. These are the only available food-supplies 

 for these plants. 



As would be naturally expected, all four sources of 

 food, namely living and dead plants, and living and 

 dead animals, are utilized by different species of fungi. 

 Those fungi which live on dead plants or animals, or 

 on the products of the decay of such, are known as 

 saprophytes: while those ihat obtain their food from 

 living sources are known as parasites. There is an 

 intermediate class, the facultative parasites, which can 

 attack some living plants, or can if necessary, live on 

 dead vegetable matter. 



Although these are the more technical divisions of 

 the fungi, they may be considered differently in their 

 relation to agriculture. In this connexion, there are 

 three points of importance. Firstly, there is the 

 damage that they cause: secondly, the advantages that 

 some of them confer; and lastly, the development of 

 which these advantages are capable. 



Some of the forms that grow on animal and veget- 

 able products — saprophytes — are a source of annoy- 

 ance and loss to man, as for example the moulds that 

 grow on grain, bread, cheese, and other eatables, or 

 even on cloth and leather. These may, however, be 

 kept in check without much difficulty. Among the 

 facultative parasites, many species can attack the roots 

 of various economic plants, and even if they do not 

 actually bring about the death of their hosts, they 

 weaken them to such an extent that the value of the 

 crop produced is greatly diminished: moreover, their 

 power of living on decaying remains of these hosts, or 

 even on those of other plants, renders them extremely 

 difficult to eradicate, once they have obtained a hold. 

 Among the class known as parasites are included all 

 those forms understood by the term Fungus in its more 

 narrow application. They are undoubtedly a source of 

 great loss to all those interested in agriculture, and 

 even when the greater part of the loss can be obviated 

 by the employment of sound preventive measures, 



the carrying out of such measures involves the expendi- 

 ture of considerable sums of money. 



On the other hand, many species are of consider- 

 able service to man, for several of them help to destroy 

 old plant and animal remains, and in this way act as 

 scavengers. They may, for example, live on heaps of 

 dead leaves, old tree stumps, decaying branches, or any 

 other accumulations of rubbish. They often possess 

 the power of secreting enzymes, which can dissolve 

 various forms of organic matter not otherwise easily 

 destructible. The products of their action go to 

 increase the humus content of the soil, often in forms 

 in which they are available to higher plants as a source 

 of food. Such fungi must be regarded as useful, both in 

 their capacity of scavengers, and in their function of 

 suppliers of humus products to various crops. Other 

 species can live on harmful fungi, and are useful in this 

 way, while still others are parasitic on various insects 

 of economic importance and are, even under natural 

 conditions, of great importance as a supplementary 

 means of keeping such insects under control. 



The recognition of this last point is of compara- 

 tively recent date, and the observations and experiments 

 that have been carried out so far tend to show that it 

 is of primary importance in the control of certain insect 

 pests in tropical and sub-tropical climates. The para- 

 sitic fungi may be readily encouraged by various means, 

 and under such circumstances afford a way of con- 

 trolling such pests, which is very much cheaper, and at 

 the same time more effective, in many cases, than any 

 of the artificial methods in common use at the present 

 time. The employment of parasitic fungi in the control 

 of various pests is at present, comparatively speaking, 

 in its infancy, but there can be little doubt that, should 

 this method fulfil in the future the promise held out 

 by the results of experiments conducted up to the 

 present time, it will prove of the utmost service to the 

 practical agriculturist. 



THE INFLUENCE OF THE STRUCTURE 

 OF SUGAR-CANE ON MILL, WORK. 



The first two part.s of Bulletin No. .30 of the Hawaiian 



Sugar Planters' Association, which presents the results and 

 conclusions gained from experiments ilesigned to ascertain 

 the influence of the structure of the sugarcane on control 

 work, as well as on the extraction of sugar, received conside- 

 ration in the last numlier of the Aijriru/tunil jfnn's. The 

 third part of the bulletin has relation to the extent to which 

 the work of mills is ati'ected by the structure of the cane. 

 Attention is first drawn to the ordinary observation that 

 increased pressure in the mill results in the proiluction of 



