The ^Yatcr of Plants and its Movements. 63 



83. To Destroy the most persistent Weeds we starve 

 the roots by preventing all leaf growth (339). 



84. Restriction of the Growth Current Promotes Fruit- 

 fulness by causing an accumulation of i^repared food in 

 the stem and branches (135 B). 



y^' 85. The Storage of Reserve Food. In healthy plants, 

 food is usually prepared faster than it is consumed by 

 growth. The surx)lus may be in the form of starch, as in 

 the potato (Fig. 16), wheat and sago; sugar, as in the 

 sugar cane, sugar maple and beet; or oil, as is cotton 

 seed, flax seed and rape. Aside from the seeds, which 

 are always stocked with reserve food, certain plants liv- 

 ing more than one year, as the potato, beet, onion, kohl- 

 rabi etc., have special accumulations of food in certain 

 parts, and the parts of plants that contain such reserve 

 food are most valuable as food for man or animals. The 

 proportion of starch stored in potato tubers is not con- 

 stant, hence the food value of different samples of pota- 

 toes may ^ai-y greatly. In woody plants, the surplus 

 food is more evenly distributed through the different 

 parts, though the older leaf- bearing wood is usually best 

 supplied. 



86. Plants Use their Reserve Food in the production of 

 flowers and seeds (135 A), and in repairing damages, as 

 the healing of wounds (73), or the replacement of leaves 

 destroyed by insects or otherwise. Annual plants (337) 

 expend all their reserve food in flower and seed produc- 

 tion and then perish as soon as the seed is rij)e. Bien- 

 nial plants devote the first season of their life to storing 

 an abundant food supply, which is expended in flower 

 and seed production the second year. Our seed crops, 



