324 



Summer Fruning of Trees-^Moislure on Plants. 



Vol. If. 



The question is often asked — if tlie seed is 

 contained in the soil, why does it only grow 

 when sown with wheat 1 I answer, frankly, I 

 that I do not know. It is tliought, however, 

 tliat the growth of one plant may somehow 

 affect the soil so as to dispose certain kinds 

 of seeds, contained therein, to vegetate— for 

 example, that the wheat crop may promote 

 the vegetation of cheat. 



Different manures may also favor the 

 growth of different seeds. A dressing of 

 ashes will cause clover, red or white, to 

 spring up in almost any soil. In places where 

 the locust tree (Robinia pseud-acacia) abounds 

 it is remarked that the seeds seldom grow — 

 yet they spring up abundantly in those spots 

 where brush heaps h.ave been burned. The 

 same remark is also true, of the common poke 

 weed, (Phytolacca decandra) and the fire 

 weed, so called from the circumstance (sene- 

 sio hieracifolius.) Now, in what way shall 

 we explain these facts] Are the plants 

 which thus spring up the mere transmutation 

 of others? or are they the fortuitous produc- 

 tions of chance f Does the ashes itself grow, 

 sometimes producing a clover — sometimes a 

 locust tree — and sometimes a poke-weed '! 

 Or does it stimulate into action the dormant 

 vegetating powers of the seeds, which pre- 

 existed in the soil? Every one will, I tliink, 

 admit the latter explanation. Experience 

 teaches that many of the hard shelled seeds 

 will sot vegetate for years, if at all, unless 

 the shell is prepared so as to admit moisture 

 to the kernel. This may be done by crack- 

 ing the shell, or by soaking in ley of wood 

 ashos, or a solution of potasli. Hence an 

 easy explanation of the effect of ashes in pro- 

 ducing plants not before observed. 



New ""Garden, 2d Mo. 24tli, 1838, 



For the Fanners' Cabinet, 



Siimsner Pruning of Trees. 



Experieiict; is ilie besl teaclicr. 

 The right time for pruning trees is after 

 the first running of the sap, from the middle 

 of June to the first week in July. The rea- 

 sons for itare — in the first place, when a tree 

 is in full leaf you can better judge what 

 branches to remove than when it is leafltss. 

 In the next, the wound heals over more kind- 

 ly and effectually after summer trimming, 

 than after winter or spring pruning ; and last- 

 ly, suckers are not so likely to shoot out after 

 midsummer trinuiiing as if it was pcrfcruied 

 in the spring of the year. The writer of this 

 has performed the opel-ation extensively on a 

 large number of trees of various kinds, the 

 last weok in June, with the greatest success, 

 and has never seen a tree, in the least degree, 

 injured by it. The practice is now becoming- 

 general among those w.ho have the most 

 iiflowledgeof the subjecf, ai«i it is hoped that 



those who are timid at departing from an old 

 custom, will make a trial of it this season, on 

 a scale proportionate to their faith, and rest 

 assured disappointment will not follow the 

 experiment. Pyrus. 



For the Fanners' Cabinet. 



Moisture on flauts. 



Dear Sir: — I was much pleased with the 

 communication of your correspondent X., 

 upon the suhiectofthe deposition of moisture 

 upon plants. The common mode of account- 

 ing for the cause why some plants show more 

 moisture than others, even of the same kind, 

 by ascribing it to greater powers of attraction, 

 I is as your correspondent observes, altogether 

 erroneous. His own explanation is doubtless 

 I correct, as far as it goes, but there is one 

 agency he has omitted to mention, the opera- 

 ! tion of which is more effective in the produc- 

 kion of refrigeration or cooling, than evapora- 

 jtion. I allude to the process of radiation. It 

 jhas been shown by actual experiments that 

 1 almost all substances in nature possess the 

 'power of throwing off heat in different de- 

 'grees, and as a general rule, those which re- 

 j fleet heat and light most rapidly, radiate or 

 [ shoot off the heat most slowly. Reflection of 

 heat is therefore a very different process from 

 radiation. The first is effected most readily 

 from bright and light colored surfaces, whilst 

 those substances which shoot off or radiate 

 heat most rapidly are usually rough and dark 

 colored. Tlius, if a piece of tin or any other 

 polished metal belaid upon a grass plot, after 

 3un-set of a clear evening, the bright metal 

 'will retain its warmth, and consequently re- 

 { main dry, whilst the grass will shoot off or 

 I radiate its heat into the clear sky, and thus 

 i become cool so as to condense the vapor in 

 I the atmosphere, just as is dons by a tumbler 

 of cold water m warm weather. Here t.hen 

 I we have the whole theory of tlie formation of 

 jdew, as beautifully explained by our coun- 

 i tryman, the late Dr. Wells. Many who have 

 not read the Doctor's treatise upon the sub- 

 j ject, or heard it spoken of, may yet entertain 

 j wrong notions relative to. the origin of dew, 

 by snpp(jsing it a light precipitation from the 

 atmosphere like a very fine rain ; or an ema- 

 nation from the ground ; but the whole pro- 

 cess is effected through t!ie agency of radia- 

 ' tion by which the plants and different objects 

 jon or near the surtiice of the earth throw oft 

 their heat in the absence of the sun, and be- 

 coming cooler than the surrounding air, con- 

 ;dense the vapor coming in contact with them. 

 ' Dew, as is well known, hardly ever forms, 

 except the atmosphere be clear and calm. — 

 I Clearness is essential to active radiation, and 

 'calmness permits the air to rest, in contact 

 I with the cooled surfaces sufficiently long to 

 1 allow of the condensation of its vapor. The 



