THE WALLFLOWER 37 



chlorophyll-corpuscles without the chlorophyll. These 

 protoplasmic corpuscles (called leucoplastids) 1 use up 

 the sugar to re-form starch granules (see Fig. 15, I). 



It is evident that the function of the leucoplastids 

 is dependent on that of the chloroplastids, for unless 

 the latter carried on the work of assimilation there 

 would be no supplies of sugar available for the use of 

 the leucoplastids. Starch is a very important reserve 

 food-substance, and is very commonly found stored up 

 in seeds, tubers, and fleshy roots, and, in fact, in organs 

 of almost every kind. It is especially important inas- 

 much as it affords the material for new cell-walls, but 

 it is used in many other ways also. Starch belongs 

 to the great group of organic bodies called carbo- 

 hydrates, which all consist of the three elements, 

 carbon, hydrogen, and oxygen, the two latter elements 

 being present in the same proportion as in water, 

 H 2 0. Sometimes we find carbohydrates stored up in 

 the form of seme kind of sugar, as in many fruits and 

 in Beetroot. These and some other forms of reserved 

 carbohydrates are always dissolved in the cell-sap. 



<y. Oil 



In many plants we find that the place of carbo- 

 hydrates is taken by various kinds of oil. Oils are 

 especially common as reserve food-substances in seeds, 



1 The word plastid is a general term, including leucoplastids , 

 chlorophyll granules, or chloroplastids, and also protoplasmic bodies 

 which contain other colouring matters (chromoplastids). The three 

 kinds of plastids are convertible into one another ; they always arise 

 by the division of pre-existing plastids. 



