SCIENCE 



[Vol. XVII. No. 428 



about 80,000 years ago. But Professor Geikie shows that 

 man, using paleolithic or rough stone implements, was liv- 

 ing in France and southern England during this last glacial 

 epoch. When the latest ice departed, permitting men to 

 extend north over Scotland and north-western Europe, they 

 had already reached their neolithic stage, using smoothly 

 ground and polished stone itnplements. 



The alternative theory of the cause of the accumulation of 

 ice-sheets, which is held by Dana, Upham, and LeConte, 

 ascribing the cold climate to elevation of the glaciated areas 

 as high plateaus, so that they would receive snowfall during 

 the greater part of the year, seems to Professor Geikie very 

 improbable, and a large portion of his last lecture was de- 

 voted to its refutation. This explanation, however, would 

 accord with the estimates of the length of post-glacial time 

 before noticed, and would seem more consistent with the 

 probable antiquity of man, and rwitli his known rate of de- 

 velopment of skill in the manufacture of implements and in 

 all the useful arts. 



TREATMENT OF FUNGOUS DISEASES.^ 



That many of the most destructive diseases of cultivated plants 

 can be and are every year almost completely controlled, is a fact 

 pei'fectly well known to those who are familiar with the subject; 

 but it lias as yet come to be reaUzed by very few, relatively, of 

 those to whom it is of the greatest importance, — farmers, garden- 

 ers, fruit-growers, florists, amateurs, and others. 



The practicability and great money value of proper treatment 

 in the case of various plant-diseases, which, in the absence of such 

 treatment, would reduce the yield of important crops to almost 

 nothing, have already become apparent to some cultivators who 

 have been progressive enough to try for themselves, or who live 

 near the experimental fields or orchards of experiment stations, or 

 of progressive neighbors. The vast majority, however, of those 

 who should be most interested have been heretofore too indifferent 

 •or too sceptical even to investigate the basis of the very strong and 

 positive statements which have been made concerning the efB.oacy 

 of preventive treatment for fungous diseases of plants. 



From the nature of parasitic fungi, and the fact that they are 

 for the most part parasites within the tissues of their hosts, it is 

 evident that our eiiorts must be directed tosvard preventing their 

 attacks. The present state of our knowledge does not enable us to 

 stop the development of a parasite within its host-plant, without 

 injury to the host, after it has once obtained a foothold. 



The various forms of preventive treatment for a given disease 

 fall naturally under two heads, — field and orchard hygiene, and 

 Individual protection. The former includes the minimizing of all 

 sources of infection by the removal of rubbish, of remains of 

 diseased plants or fruits, or of wild plants which may serve as 

 propagators of the disease. The latter includes the application to 

 the plants to be protected of substances in liquid or solid form 

 which shall fortify them against the attacks of fungi which cause 

 disease. Such substances are known as " fungicides." Since 

 different fungi attack their hosts in very different ways, since 

 their modes of development and the effects which they pro- 

 duce differ widely, it is plain that no all-embracing rule can be 

 laid down tor the treatment of fungous diseases. Certain princi- 

 ples of general applicability can, however, be stated, certain gen- 

 eral directions can be given, and insti-uctions regarding the prepa- 

 ration and application of those fungicides which have been proved 

 to be most useful and effective can be furnished. 



There are deflinite laws of health for plants as well as for ani- 

 mals ; and in one case, as in the other, neglect of those laws invites 

 disease. In the first place, plants which are expected to grow 

 and thrive must be furnished with an abundance of the materials 

 necessary to growth. Weak, poorly nourished plants suffer the 

 attacks of parasites of all sorts, and have no power to resist them. 

 Second, where a crop has suffered from a fungous disease in one 



! Abstract of Bulletin No. 39 ot the Massachusetts State Agricultural Exper- 

 iment Station, tor April, 1891, by James Bills Humphrey. 



season, and a good crop of the same kind is desired in the follow- 

 ing season, every tangible trace of the disease must be removed. 

 For example : if a vineyard has suffered from mildew or black rot, 

 all diseased leaves and berries should be collected at the end of 

 the season with scrupulous care, and wholly burned ; and the same 

 advice applies to a large list of cases. Thus incalculable numbers 

 of the spores of the fungi of the respective diseases will be pre- 

 vented from infesting the next season's crop. In some cases 

 where the spores remain in the soil, as in the stump-foot of cab- 

 bages or the smut of onions, the attacks of the disease can only be 

 avoided by rotation with crops upon which the fungus in question 

 cannot live. Third, wild plants, which, being nearly related to a 

 given cultivated one, may be subject to the same disease, or which 

 bear a complementary spore-form of a pleomorphic fungus, should 

 be carefully excluded from the neighborhood of cultivated ones. 

 Thus, wild cherries or plums, wliich are equally subject to the 

 black- knot, should be kept away from plum-orchards, and spinach- 

 fields should be kept free of pig-weed, since both plants are 

 attacked by the same mildew ; and again, since red cedars bear 

 one spore form of a fungus whose other form is the rust of apple- 

 leaves, it is plain that they should not be allowed to grow near an 

 apple- orchard. 



Now, when the general hygienic conditions have been made as 

 unfavorable as possible to the development of disease, we may re- 

 sort finally to the special protection afforded by the use of fungi- 

 cides. 



These preparations, when properly prepared and when applied 

 at the right times and in the right way, have been abundantly 

 proved to be of the greatest value, and often to determine the dif- 

 ference between a full crop from plants on which they are used 

 and practically no crop where they are not applied. 



But the fact cannot be too strongly emjihasized that every thing 

 depends upon how they are prepared, and upon how and when 

 they are applied. The bulletin gives somewhat full instruction 

 how to prepare and apply the most valuable fungicides, and such 

 general hints when to apply them as will be of service. The 

 proper times for their application vary so much with special 

 conditions, however, that instructions on this point must form 

 an important part of the special directions for any particular 

 case. 



The protective quality of most of the best fungicides lies in the 

 fact that they contain a certain proportion of copper; and, of the 

 four recommended as applicable to most cases of fungous diseases, 

 three contain it as the essential constituent. 



The Bordeaux mixture requhes six pounds of sulphate of cop- 

 per, four pounds of quicklime (fresh), and twenty-two gallons of 

 water. 



The sulphate of copper, known to the trade also as blue vitriol 

 or blue-stone, is dissolved in two gallons of water. The solution 

 will be hastened if the water be heated and the sulphate pulverized. 

 After the solution is complete, fourteen gallons of water are added 

 to it. The quicklime is slaked in six gallons of water, and stirred 

 thoroughly until it forms a smooth, even mixture. After standing 

 for a. short time, it is again stirred, and added gradually to the 

 sulphate solution, which is thoroughly stirred meanwhile. The 

 mixture is then ready for use, though some experimenters recom- 

 mend further dilution to twenty-five or thirty gallons for certain 

 uses. It should not be prepared until needed, and should be used 

 fresh, as it deteriorates with keeping. Since the lime remains 

 merely in suspension, and is not dissolved, the mixture should be 

 strained through fine gauze before entering the tank of the spray- 

 ing-machine, so that, all of the larger particles which might clog 

 the sprayer may be removed. 



Ammoniacal carbonate of copper, in its improved form, is pre- 

 pared from three ounces of carbonate of copper, one pound of 

 carbonate of ammonia, and fifty gallons of water. 



Mix the carbonate of copper with the carbonate of ammonia, 

 pulverized, and dissolve tbe mixture in two quarts of hot water. 

 When they are wholly dissolved, add the solution to enough water 

 to make the whole quantity fifty gallons. This preparation has 

 been found to be better and cheaper than that made according to 

 the original formula, which is as follows : — 



Dissolve three ounces carbonate of copper in one quart aqua 



