CHAPTER XI 



PLANT PRODUCTS 



PLANTS produce a great many compounds, some of which be- 

 come permanent structures in the plant, others are used directly 

 in the processes, of growth, others are stored for use by -the plant 

 at some future period and still others are believed to be by-prod- 

 ucts or waste so far as the welfare of the plant is concerned. 

 Many of these plant products have been utilized by man for 

 foods, clothing, building, fuel, drugs and other purposes. The 

 products include both the cell walls and cell contents. The cell 

 contents may be divided into the protoplasmic and non-proto- 

 plasmic products. 



Protoplasmic cell contents are the protoplasm, nucleus and 

 plastids which have already been considered (see Chapter I). 



Non-protoplasmic cell contents are (1) those of a definite 

 form, including (a) the colloidal or crystalloidal products, such 

 as starch and inulin ; (6) the crystalline products, such as sugars, 

 alkaloids, glucosides and calcium oxalate ; the composite bodies, 

 such as aleurone grains, which are composed of different 

 compounds ; (c) those of a more or less indefinite form, such 

 as tannin, gums, mucilages, fixed and volatile oils, resins, 

 gum-resins, oleo-resins, balsams, caoutchouc, silica and cal- 

 cium carbonate. 



- " Starch is the first visible product of photosynthesis " (see 

 page 195), although it is no doubt preceded by the formation of 

 sugar. Starch grains are formed within the chloroplastids, but 

 they sometimes become so large as to break the covering mem- 

 branes of the plastids. Starch may be made soluble by the action 



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