HAY-TIME 151 



of the haulm the knots become crowded. Here 

 the unequal turgidity l of the cellular tissue can be 

 turned to good account. That side which comes next 

 to the ground swells, while the opposite side becomes 

 compressed or even folded. When a haulm has been 

 pushed out sideways from the rootstock it is the unequal 

 turgidity of the knots which causes it to curve 

 upwards and take an erect position. After a storm of 

 rain and wind has laid the long stalks, the turgidity of 

 one side of the knots (always that side which comes 

 next to the ground) erects it once more. The 

 deflection capable of being produced by a single knot 

 is only moderate, but as the knots are crowded together 

 at the base of the haulm, a considerable aggregate effect 

 can be brought about. Inclination through an angle of 

 ninety degrees can be caused by the unequal turgidity 

 of three or four knots. 



Thickenings containing tissue \vhose turgidity can 

 bs regulated are found also at the points where the 

 inflorescence of a grass branches. It is by means of 

 such organs that the lateral stalks, the flowers, and 

 even the bracts of the flowers, change their posture as 

 required. In the bud all the flower-stalks are limp 

 and collapsed, but when the flowers ripen the stalks 

 take up the most favourable position, often at right 

 angles to the haulm. Turgidity, or the want of it, 

 regulates the exact place and attitude of every mem- 

 ber of a highly complex inflorescence. 



Additional roots are often emitted from the lower 

 knots of a grass-haulm. They push out through the 

 leaf-sheath, which is ruptured to give them passage. 

 1 Turgidify is distension of the tissues by water. 



