42 BOTANY 



organic compound, starch, is called carbon assimila- 

 tion, and it is only possible for it to take place in 

 those parts of the plant where the cells are green, or 

 rather, it only takes place in the cells which contain in 

 their protoplasm small green bodies called chloroplasts. 

 These chloroplasts, by reason of their colouring matter, 

 are able to use and convert the energy of the sunshine 

 to supply the chemical energy necessary to cause the 

 combination of the elements that form the starch. 

 In the darkness the leaves are like a factory in which 

 the engines have been stopped and nothing can be 

 done. It is only in the light, with a supply of the atmos- 

 pheric gases and of water, and with the green bodies in 

 a healthy condition, that the manufacture of food can 

 go on. Some plants, or parts of plants, do not appear 

 green, but are red or some other colour, as in the case 

 of the red seaweeds for instance. This does not neces- 

 sarily mean that they are not producing their food, for 

 sometimes coloured sap or other granules mask the 

 chlorophyll in the cells, but without interfering with 

 their activities. On the other hand, some coloured 

 plants, such as the brilliant toadstools, for example, 

 are not able to make any food at all, for they are funda- 

 mentally devoid of the chlorophyll grains. Such plants 

 can only get their food by stealing it from some living 

 green plant, or by using what is left in the protoplasm 

 of dead ones. Such chlorophyll-less plants correspond 

 to animals in their nutrition in that they have not the 

 power to work up the simple elements for themselves. 



Important in nutrition as are the carbohydrates, the 

 manufacture of which we have just indicated, they are 

 not alone enough for the nutrition of protoplasm, 

 whether of plant or animal. Some nitrogen and a few 

 mineral salts among which iron, phosphorus, potassium, 



