ILLINOIS HORTICULTURAL SOCIETY. 263 



lint assiiiiiin^' tli;it siicli parnUcls exist lictwccii aiiiin;il ami vc^'ctaliif ]iliy^i<'l"fi'y, is no i)rool' tliat 

 tlifv lilt I'xist: ami tlic prcml' ticlii^ tliat tiicrc is no rcpiilar ilownwanl How of sap at ail, ami lliat the 

 upward How <lcpcuils upon tenipi'iatnic. leaf ovajiorat ion. ami other inleiiiiitteiil <'auses, llie idea of 

 a I'C'uniar How in tlie sense of the eircnlation of tiie lilood must lie aliamloneil. 



True, the i)lant food from tlie soil passes up and to all i)arts of the plant : and tiW' i)lant food froui 

 the ail" i)asses down, an<l alilie to all parts of tlie i)lant; hut all tliis food i)asses from cell to ceil, 

 tlirouffh tlie apparently contimums cell walls, ami does not How in streams, l)ut simply ditfuscs Itself 

 liy "osmose"" or ••mendirane ditt'usiou.'" 



The power of tlie cell meml)raues or walls to absorb and f;ive out ii(iuids, called osmose, may 

 explain some of tlie plienouieiia of firowlli, liiit will not account for all the acts of tlie firowiuj;- plant, 

 so we must acknowled};<' auolher force, namely, that of cliemical selection. ]f all the reipiired sub- 

 stances for tlie jtlaiifs frrowtii existed in tlie soil, oi' in tlie air, in a state of solution, or as fiasses, 

 the tlieory of membrane diHusion mi>;lit explain how and wliy they lind their way to every ])art of the 

 plant : liut many of the suiistaiiees recpiiieil liy tlie plant are not in a s<duble state in llie soil, and bein^' 

 soliils tliey cannot enter the plant witlioiit bein^lirst dissolvi'd. Talcc silica, for example. Tliere is 

 no evidence to sliow tliat soluble silica exists in all tillable soils; in fact, it is very rarely found in 

 nature in the soiulile slate: and yet an analysis of tlie ash of most idaiits reveals its presence, sonie- 

 times to the extent of 7;'i-IiKltli of tlie wlnde ash. How does this insoluble sulistame tind its way into 

 the plant and there become ail element of its fiTowthy Clejirly the plant itself attacks and dissolves 

 silica out of the soil by virtue of its jiower of chemical selection, (iraiit, once, that a phiiit lias witiiiii 

 itself a power of deconiiiosiiif!: chemical compounds, of renderiuf;- soluble naturally in.soiuble liodies, 

 and of selectiiifi' food, and you exjilain the one jrreat mystery of plant nourisliment, iianiely: how the 

 iiisoliilile s<iil is transformed into or;:anic bodies. Recent experiiiieiils conclusively show the select- 

 ive power of plants: where, for examiile. plants were ^irown in solutions having!- a known chemical 

 character. As firowtli projiressed a constant cliaii;;e in ciii'inical coiii|>ositioii was observed to take 

 place, soon renderiiiff the solutions unfit for the liirtlier .uppoil of tlie iiiant, ami even iiosiliveiy 

 destructive. 



I'rof. .lolinsou says tliat '•The roots of a plant liave the |iower to decompose salts— e. ;;. : nitrate of 

 potash and cliloride of amimniiuui— in order to aiiiiropriate one of their ingredients, tlie other being 

 rejected." 



With these facts in view, we may readily see why soils are so stranj^ely altered by continual crop- 

 pin^'. First tlie roots use up certain parts of tlie soil, and secondly, they f-ive rise to new bodies— 

 their refuse or rejected matter. 



Here are two ^:ood reasons for rotation of crops. One crop brings its power of chemical selection 

 to bear upon the soil till the material to act upon runs short, when another kind of ffrowtli may 

 step in ami liinl food from tlie original iii}ire<lients of tlie soil and also from the liodies resulting- from 

 the cliemical selection of tlie former croj). ,Vii apple tree may exhaust a soil for apple culture, and 

 still leave beliiiid the very substances most needed for a puinpkin vine. One thought further in 

 reference to Mr. Foster's Krrors in Horticulture, and 1 will leave this part of nn subject. It 

 appears to me tliat the jireatest error in that jiaper is not an error exjiosed but an error coiii- 

 niitled. And it is tliis: That the surface of the larger, older roots absorbs plant food as wi^U as the 

 smaller, anil hence it is lietter to cut oil the libroiis ro(ds in transplantinj;'. 



Tile iarfic roots of perennial plants are not capable of taking up food to any j;reat extent, nearly the 

 whole nourisliment of the plant beiiij; absorbed by the small yoiiii{r roots. This fact may be easily 

 demonstrated with a microscope, wliich will sliow layers of empty dead cells coveriiij^ the whole sur- 

 face of the old roots and iireventiii};' absorplion, while the youiij; roots in the growiiiff season have a 

 surface of live, absorbent cells, from which the jirocesses called root hairs project, tliereby ;;reatlv 

 extending' the absorbin;!' surface. Hence, if the yoiiiifr roots are not injured, we sliould keep them: 

 liiit if injured, they should of course be pruned away. I now come to the ^iraiul i|iiestioii which 

 oversliadows all others in vcfietable jihysiolojiy, namely: to what extent, and in what manner, may 

 we impress the life principle or organic force of plants. 



This ipiestioii covers the whole jiroiiiid of plant culture, fertili/.inj; tlie soil and the jiroiluctioii of 

 new and improved varieties. We know, inajreneral way, that plants vary in a natural condition, 

 anil we know further that they v:iry still more under doinesticatioii, but every elfort to discover the 

 exact causes of variation has so far lieen futile. W'c can by c;irefui selection and breediii;;, secure a 

 larger aglRregate of \ariatioii after the specific variation lias once comineiiced; but who lias by any 

 treatment potentially originated a trail of character jiossessed by none of the plant's ancestors. 

 Thousands, millions of impro\ed varieties ha\e been originated somehow, but no man dure say "I 

 did It." The most carefully conducted artificial hybridizations are by no means certain as to results 

 not even certain always to iirodnce ottspring reseinbiing either parent. 



Darwin in the "Variations of animals and jilants under domestication.'' has mill tijil led proofs and 

 deductions, but nowhere does he tell us liow to impress the vital force so that a certain seed shall 

 produce a tiower witli a new sjiot upon a certain petal. 



Every act done to a jilaiit which modiHes it or its oti'spring in form or any other respect, is an 



