io8 



BOTANY OF THE LIVING PLANT 



may also be used in supply of material for cell-walls, and in other 

 ways. Thus the immediate needs of the growing plant for the 

 production of new tissue are met. 



D 



STORAGE. 



Since under favourable conditions Photo-Synthesis is a relatively 

 rapid process, it will commonly happen that material is gained more 

 quickly than it is used up. The balance is then stored for future use. 

 It may be laid aside in ordinary normal tissues, and this is the usual 

 condition. Any parenchymatous tissue may serve. For instance, 



in trees which drop their leaves 

 A in autumn and form a new 



i--f suit of them in the spring, the 



material for these is prepared 

 in the previous season, and 

 stored in the trunk and 

 branches. It is laid aside 

 chiefly in the medullary rays 

 and the wood-parenchyma, as 

 well as in the parenchyma of 

 the cortex. Accumulations of 

 it may even be made for a 

 series of years as in the Beech, 

 which flowers only at intervals 

 and then profusely, depleting 

 the store. But in many cases, 

 especially in herbaceous plants, 

 storage is effected in parts 

 specially distended for the 

 purpose, as in the turnip, carrot, and potato, or in the swollen roots 

 of the Dahlia; or, again, in the fleshy leaves of the Onion and other 

 bulbous plants. Lastly, in seeds material is habitually stored, which 

 is provided by the activity of the parent plant to meet the needs of 

 the seedling in the first stages of germination. Storage, in one form 

 or another, is then a common phenomenon in plants. 



The materials thus stored fall under three heads : (i) Carbohydrates, 

 (2) Fats, (3) Proteids. The first and second of these are non-nitrogenous, 

 and may be regarded more particularly as formative materials for 

 cell-wall. Materials of the third class are nitrogenous, and may be 

 held as more directly formative for protoplasm. The Carbohydrate 



FIG. 77 bis. 



Starch grains from the Potato. A, simple ; B, half 

 compound ; C, D, compound grains. c, organic 

 centre, or nucleus of formation. ( x 540.) (After 

 Strasburger.) 



