OETTINe ESTABLISHED 



11 



about four inches deep and pack clayey soil firmly 

 upon them. How long before they appear above 

 ground ? Do they come up through the cracks (espe- 

 cially at the sides), or not? Sometimes they lift up 

 the whole mass of earth as a solid cake and thrust 

 it out of the pot. After witnessing a feat of this sort 

 we are more ready to believe the tales 

 about mushrooms which lift flagstones 

 and the like. 



In what part of the stem is the force 

 developed which makes these feats pos- 

 sible? Bend a piece of wire (about three 

 inches long) into a V, and connect the 

 ends by a fine thread (a single strand 

 taken from a silk thread) so that the latter 

 will be stretched taut; moisten this with 

 India ink ; hold a cardboard scale (or 

 ruler) against the stem and mark the stem 

 at intervals of exactly one -eighth of an 

 inch by touching it with the inked thread ; 

 stems devoid of hairs are- most easily 

 marked (Fig. 63). The growth of the stem will cause 

 the ink marks to separate, and the degree of separation 

 will indicate the place of most rapid growth. Where 

 is the region of most rapid growth ? How long does 

 the growth continue most rapid in this particular re- 

 gion ? How long does this region continue to lengthen ? 

 How much of the stem is growing at a given instant ? 



63. Bean with the 

 stem marked, in 

 order to deter- 

 mine the region 

 of greatest 

 growth. 



