180 THE FLORIST AND 



foliage which is young and growing, and, consequently, two distinct pro- 

 cesses are going on at the same time within them, which operate in opposi- 

 tion to each other. By the mature leaves, carbon, under the influence of 

 light, is taken up from the surrounding atmosphere, and arterial sap is 

 generated. The young and immature leaves, on the contrary, vitiate the 

 air in which they grow by throwing off carbon ; and they expend, in adding 

 to their own bulk, that which ought to be expended in the creation of shoots. 

 This circumstance respecting the different operations of immature and 

 mature leaves upon the surrounding air, presented itself to the early labor- 

 ers in pneumatic chemistry. Dr. Priestley noticed the discharge of oxygen 

 gas, or dephlogisticated air (as it was then called), from mature leaves. 

 Scheele, making, as he supposed, a similar experiment upon the young 

 leaves of germinating beans, found these to vitiate air in which they grew. 

 These results were then supposed to be widely at variance with each other, 

 but subsequent experience has proved both philosophers to have been equally 

 correct. 



I possess many seedling young trees of the Ulmus campestris, or suberosa, 

 or glabra ; for the widely varying characters of my seedling trees satisfy 

 me, that these three supposed species are varieties only of a single species. 

 One of these seedling plants presented a form of growth which induced me 

 to wish to propagate from it. It shows a strong disposition to aspire to a 

 very great height, with a single straight stem, and with only very small 

 lateral branches, and to be, therefore, calculated to afford sound timber of 

 great length and bulk, which is peculiarly valuable, and difficult to be 

 obtained, for the keels of large ships ; and the original tree is growing with 

 great rapidity in a poor soil and cold climate. 



The stem of this tree, near the ground, presented, in July, many very 

 slender shoots, about three inches long. These were then pulled off and 

 reduced to about an inch in length, with a single mature leaf upon the upper 

 end of each, and the cuttings were then planted deeply in the soil. The 

 cuttings were then covered with bell glasses in pots, and put upon the flue 

 of a hot-house, and subjected to a temperature of about 80 degrees. Water 

 was very abundantly given, but the under surfaces of the leaves were not 

 wetted. These were in the slightest degree faded, though they were fully 

 exposed to the sun ; and roots were emitted in about fifteen days. I sub- 

 jected a few cuttings taken from the bearing branches of a mulberry tree to 

 the same mode of management, and with the same result ; and I think it 

 extremely probable, that the different varieties of Camellia, and trees of 



