DIVISION OF GARDENS AND GEOUNDS. 39 



It lias been recorded that in some seasons only certain varieties of 

 poaclies in an orcbard will be affected with leaf blister, while other va- 

 rieties are nnbarmed. Then, again, dnriiig" a subsequent season, tlie 

 varieties previously attacked will be unharmed, while those foriucrly 

 exempt from the disease will be allectetl. Tliis is accounted for by the 

 condition of the growth at the time of a sudden injurious chirfige of 

 temperature. There is a certain period when the young leaves are most 

 susceptible to such changes, and as this period is not reached at the 

 same time by all varieties, some being earlier than others, it follows that 

 some are injured while others escape. 



It is also well known that in some seasons there are no blistered leaves 

 to be found on any variety, the climatic conditions not being favorable 

 to the development of the fungus. 



There is much in connection with the appearance of mildew on the 

 foliage of plants which would indicate that it is in most cases the result 

 of cold or aridity in the atmosphere, or, perhaps, rather in their com- 

 bined action. This seems to be more particularly observable in fungi 

 of the Erijsiplie class. The foreign grape-vine, as well as many other 

 European plants, such as the hawthorn, lilac, &c., when subjected to 

 our dry, hot atmosphere, suffer much from mildew. Even when the for- 

 eign grape is grown in glass structures, the utmost care must be taken 

 in regard to ventilation during summer in order to avoid Erysiplic on 

 the foliage; the admission of the outer air when it is 20° to 30° below 

 that of the house will certainly afi'ect the young leaves, at least those 

 nearest the ventilator. It is a common observation that young roses 

 may be kept during the winter in a pit or frame, where for weeks or 

 months they receive no ventilation whatever, but as spring advances 

 and the increase of temjierature necessitates ventilation, then mildew 

 makes its appearance on the leaves. It may be said that this is the re- 

 sult of careless management in the method of admitting the outer air to 

 the plants, but, nevertheless, the best of management will not always 

 prevent it. 



A very dry air acting on tender leaves will cause an excess of evap- 

 oration which will produce cold on their surfaces ; it is, therefore, per- 

 haps more than a mere hgure of speech to say that the appearance of 

 Erysiphe on the leaves of plants is an evidence that, by some means or 

 other, the plant is suffering from the eflects of cold. 



The disease called yellows has long been known ; indeed, it is more 

 than probable that the disease manifested itself upon the first attempts 

 at the culture of the peach in this country. Amherst College authori- 

 ties state that it was destructive in Massachusetts one hundred and 

 twenty years ago. The cause of the disease has been a matter of uncer- 

 tainty since its first discovery, and the various opinions which have 

 been expressed regarding it can hardly be enumerated. The exhaustion 

 or original deficiency of certain elements in the soil has been, and stiU 

 is, a popular explanation as to the cause of yellows, but what particular 

 ingredient or ingredients are lacking, provided that this is the cause, 

 may be a matter of opinion. Dr. Goessmann, of Massachusetts Agri- 

 cultural College, gives the following formula as a preventive, viz: 

 400 pounds of acid bone phosphate, containing 50 pounds phosphoric 

 acid ; 150 to 200 pounds muriate of potash, containing 100 pounds pot- 

 ash; 100 pounds crude sulphate magnesia. This is worked in the soil 

 for a distance of 10 feet about each tree. From experiments made at 

 Houghton farm, the following mixture of commercial fertilizers is rec- 

 ommended as not only preventing but curing the disease, viz : 25 pounds 

 Kieserite, 100 to 160 pounds muriate of potash, and 450 pounds dissolved 



