254 Mississippi Valley Horticultural Society. 



1. Organic — Structural, including variety and manner of growth. 



2. Geological— Soil formation. 



3. Climatic — Temperature, saturation, moisture. 



4. Location — Including aspect and elevation. 



5. Culture — Including pruning and general care. 



That woody growths differ in their organic structure is a matter of com- 

 mon observation. But to show the relation between .such differences and 

 capacity for enduring climatic changes has been too generallj' overlooked by 

 scientific observers. Wood}- structure is made up of vegetable fiber, which 

 holds the sap in various stages of development towards organized matter. 

 This vegetable fiber contracts with cold, while the sap expands with any de- 

 gree of cold sufficient to congeal it (pure water expands below 89° F.). This 

 contraction and expansion is a severe strain upon the cellular structure of a 

 tree, and a rupture of its cells jiroduce some form of disease. >sow, the ca- 

 pacity of a tree or plant for enduring repeated extremes of temperature, or, 

 in common terms, hardiness, is measured bj' its toughness or strength of 

 fibre, and the size of its sap vessels. 



Thus a section of Rhode Island Greening shows a much larger proportion 

 of porus wood than the native crab, and equal sized sections of each variety, 

 dry, will show a difference of twenty (20j per cent, in weight in favor of the 

 crab w'ood. The same will hold good with all wood growth of a given species 

 and climate. There will be found a corresponding difference in their ca- 

 pacity to resist the changes of temperature as indicated in this test, allowing 

 something for the operation of the vital force in all cases. 



The question of " vital force " is one on which science is at variance. Some 

 claim that there is no inherent vitality, but that organized matter is built up 

 and lives by a general law of growth, or " matter in motion." Whatever 

 may be the true theory of life or action in organized matter, we know that, 

 while individuals differ largely in their native vigor and endurance, the va- 

 riety or species show much greater variation in this respect. 



Thus, we have the hard woods of the South, of which the live oaks, the 

 Citrus family and the Maclura are examples of extremely close-grained wood, 

 yet very sensitive to cold, and for still another reason, because they never get 

 ready for it, but prolong their growth indefinitelj'. I believe we may meas- 

 ure the enduring powers of a given species by the size of its capillary cells, 

 the toughness of its fiber and its natural season of growth. 



On the question of soils, our State Geologist remarks: " The most reliable 

 natural indications of the agricultural capabilities of a district are to be 

 found in its native vegetation. The natural flora may be regarded as the re- 

 sult of nature's experiments in crop-raising through the thousands of years 

 that have elapsed since the region became covered with vegetation." 



Science as well as experience shows that lime and magnesia are indispen- 

 sable elements in the production of fruit. And so we see that our whole 

 .series of limestone soils are well adapted to the healthy development of the 

 api)le-tree and the production of the finest fruit; and they are, in these re- 



