92 



I'LAKT STUDIES 



As is well known, when a seed germinates the tip that is to 

 develop the root turns towards the earth, even if it has 

 come i'rom the seed in some other direction. This earth 

 inllnence is known as (jeotroplsin. Another directing" in- 

 lliience is moisture, or the water influence, known as hijdrot- 



l^-~~^ r 



Vn;. sr. A srctinn tliriiiiuli the IcMf-stalk nf a yiAitny iJOiHl-lily i Xiip/iai), Rluraing the 

 nnnicrniis cfnispiiiioiis air ]ia^sai.a's (,s'l tiy means of which the parts iliaier waler 

 are arrateil ; /;, inhaiial liaiis iirnjeelin^ into tlie air jaissa^'es ; r, tlie uincli 

 rediifeil and eninparalively few \asenlar laindlrs. 



ropism. By means of this the root is directed towtirds the 

 most fa,vorahle water supply in the soil. 



Ordinttrily. gcdtrojiisnr ;ind hydrtif ropism direct the root 

 in the same general wa,y, a.nd sk reinforce I'tich otluT ; hut 

 the following cxpci'liiieut may he arrtingcd. which will 

 separate these two inlliicnces. Ilorc scverttl small holes iu 

 the Ijottom of ii, lio.x (such tis ti cigar liox), stispendcd as in- 

 dicated iu Figure S."i, aJid cover the hottom with hlottiug 

 ])aper. Pass the root tips of several germinated seeds 



