AMERICAN POMOLOGICAL SOCIETY. 



In continuing our notice of the Nadonal Society, 

 we now give the able address of Mr. A. Fendler. 

 To our mind it is one of the most philosophical ever 

 presented to any of our Horticultural societies, and 

 calculated to aid materially in arriving at a satisfac- 

 tory theory of some of our worst plant diseases ; 



ADDRESS BY A. FENDLER, OF ST. LOUIS. 



A microscope of good magnifying power reveals 

 to us the fact that every part of the organized fabric 

 or tissue of trees and plants consists of a multitude 

 of separate cavities, Any slice of the root or other 

 part of the plant, thus magnified, presents somewhat 

 the shape of a honeycomb, and is, in fact, an aggre- 

 gate of more or less elongated little bladders, or sacs 

 called cells. 



The whole potentiality of the plant exists in the 

 individual cells of which it is made up. In them its 

 products are elaborated, and all the vital operations 

 carried on. The young and most vitally active cells 

 are found between the wood and the bark, and in all 

 parts of recent growth, such as buds, young shoots, 

 and rootlets. In these active cells, the transforma- 

 tion of the crude sap into new vegetable tissue is 

 perfornjed. 



Water is the vehicle by which the great bulk of 

 the plant's food is convej^ed ; first through the root 

 and subsequently through the active cells of the 

 whole plant. This conveyance is either retarded or 

 accelerated, according to the less or more vigorous 

 perspiration of vapor through the surface-pores, 

 and exhalation from the breathing-pores of the 

 leaves. In the interesting experiments of Dr. Hales, 

 a vine, with a surface of foliage equal to twelve 

 square feet, exhaled or perspired at the rate of five 

 or six ounces of water a day. This, of course, is 

 during the period of active vegetation, and in dry 

 weather. 



The breathing-pores are situated, principally, on 

 the lower side of the leaves, and so arranged as to 

 afford free communication between the external air 

 and the whole interior space of the leaf. They are 

 a kind "of safeguard against excessive evaporation 

 in dry weather ; they open only when they are 

 moistened, either on the inside or outside, and con- 

 tract when dry on hoth sides, so that if the plant 

 contains an abundance of moisture, these breathing 

 pores remain open and allow it to escape; but when 

 the plant, in dry weather, suffers for want of mois- 

 ture, the breathing pores close up. Yet they will 

 also open, if moistened from the outside alone, no 

 matter how dry the plant may be inside, and thus 

 the superabundant humidity of the atmosphere 

 may find its way far into the tissue of the plant 

 by what meteorologist call "the force of vapor." 



We all know the powerful pressure of heated 

 steam, as daily exhibited in the piston-rod of steam 

 engines. This is done by the repelling force of the 

 heated particles of aqueous vapor. The more heated 

 and crowded they are, the greater their repelling 

 force will be. 



But even vapor of a loio temperature exerts a 

 certain amount of pressure that can be made mani- 

 fest and measured. It makes no differenc whether 

 the vapor is heated artificially or by the sun ; it al- 

 ways presses in proportion to its density and tempe- 

 rature, even when free and unconfined as in the 

 open atmos{)here. It presses not only through the 

 breathing pores of the leaves, but also through 

 the common pores of the bark of tender shor.ts, 

 and the pores of the skin of young fruit, and enters 

 the interior of the plant, — provided the plant is 

 comparatively void of moisture, and the atmosphere 

 saturated with it, and of a high temperature at the 

 same time. 



In our climate of the Mississippi valley, and fur- 

 ther East, this state of the atmosphere may often 

 be noticed during the months of June and July, the 

 aqueous vapor being supplied by the moisture bear- 

 ing southeast and south-southeast winds. The lower 

 strata of the atmosphere are then charged with a 

 superabundance of humidity in the state of invisible 

 vapor. 



If, at this period of hot, sultry weather, showers 

 of rain are scant and far between, not sufficient to 

 keep the soil in its normal state of moisture, the 

 roots of a plant may be languishing for want of 

 water, at the same time that its over-ground part 

 is immersed in a bath of warm vapor. This im- 

 mersion, though stopping the evaporation from, the 

 leaves, does not matter so much, as long as the 

 roots have a sufficiency of moisture. For this mois- 

 ture, imbibed by the roott and carried up to the sur- 

 face of the leaves, will, in the form of vapor or steam 

 effectually hinder the outside steam from entering 

 the tissue of the plant. But when there is no mois- 

 ture in the ground, the outside steam encounters no- 

 thing to oppose its own force, and will have free 

 access through the pores of leaves, berries and young 

 shoots. 



It may easily be imagined that this reversed 

 course of nature is of no advantage to vegetation ; 

 on the contrary, it cannot be but highly injurious. 

 How would men and animals prosper if, instead of 

 receiving their daily liquid and solid food through 

 the mouth and stomach, they were treated unremit- 

 tingly for days and nights to a bath of warm vapor, 

 though that vapor contained a liberal admixture of 

 some nourishing volatile ingredients? Far better 

 for the system, both animal and vegetable, to re- 



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