314 TKANSACTIONS OF THE HORTICULTUEAL 



been different, and the books are full of means by which their del- 

 eterious influences may be avoided. But, as a general rule, the means 

 are too costly or too inconvenient for wide ajjplication, even where 

 the habits of the people and the cost of lalior in every way favor it. 



The same is true of the experience in this country so far as any 

 has been had. We refer to the plan of Mr. William Saunders for 

 preventing loss of radiation from the vine, and hence both dews and 

 frosts, consisting of a simple covering with boards. This simple 

 means would doubtless be considered too costly in extensive vine- 

 yards. The fact is that with this, as with all other meteorological 

 conditions that continually prevail and have an injurious influence,^ 

 we have no satisfactory means for combatting them. They must be 

 considered as necessary evils, and where they prevail the labor that 

 would be bestowed upon the vine must be given up for that purpose^ 

 and be directed into other and more profitable channels. To fix the 

 standard for each culture and each section by the combined observa- 

 tions of the meteorologist and horticulturist is an end devoutly to be 

 wished. 



Vegetable physiologists have also told us that in common with 

 vegetation, with proper conditions of temperature and moisture, and 

 Avith suitable supplies of nutrition at the disposal of the vine, light is 

 the all-important factor in the determination of those changes within 

 its members which constitute its physiological functions. The 

 actinic power of light, or its power to cause chemical changes, causes 

 the absorption and assimilation of carbon from the air through the 

 green matter or chlorophyll, and the consequent production of the 

 carbhydrates — starch, sugar, etc. — upon which the value of the fruit 

 depends. Within the leaves these compounds are formed through 

 the intervention of chlorophyll under the influence of light — starch 

 first, then its soluble modifications, which finally yield the sugars and 

 acids, which maybe transported through the cell tissues to be used up 

 in the development of other parts of the vine, in the development of 

 the fruit, or to be stored up for the future demands of the vine and its 

 fruit. Both vegetable physiology and chemistry teach that there is- 

 a definite relation between the extent of the leaf surface and the 

 quantity of sugar and other carbhydrates developed within the plant. 

 Macagno has shown that extensive reduction of the leaf surface of 

 the vine produces also a reduction of the sugar developed within the 

 fruit. He also found that light is an important factor in the de- 

 velopment of the more desirable qualities of the fruit. To determine 

 this fact he set apart three sets of vines — one set he covered with a 

 black cloth; another set he covered with a white cloth; the third was 

 left in the normal condition. The light was not cut off entirely, but 

 it was very much diminished, in the first case more than in the sec- 

 ond. The temperature that prevailed were: Under black cloth, 93° 

 F.; under white cloth, 81° F.; in open air, 70° F. The effects of this 

 treatment were noticed very early it the season, and were very 



