1S89-90] 21 3 



teresting to watch this process under the microscope, and it can 

 be easily observed in the cells of the American weed, stinging 

 hairs of nettles, &c. In the desmid a little group of granules 

 keep up a slow but continuous motion round and round, but 

 what this motion is for, no one knows. The structure and 

 use of leaves in the life of a plant were then explained and 

 illustrated by a section of the common Liverwort, showing the 

 pores or Stomata which were found in great numbers on the 

 surfaces of leaves. Their green colour arose from the grains of 

 chlorophyll contained in their cells. These green parts were 

 not only ornamental, but were also the most useful and hard- 

 working parts of the whole organism. Leaves correspond more 

 or less to lungs ; for the chlorophyll has in sunlight the power 

 of assimilating carbon from the atmosphere ; and when it is re- 

 membered that there is only -04 per cent, of carbon dioxide in the 

 air, and that half a plant's weight is made up of carbon, the 

 enormous work they do is apparent. Chlorophyll was truly a 

 wonderful substance, and did a mighty work in nature. These 

 little grains were the manufactories of the plant, mills to grind 

 its corn, teeth to masticate it, stomachs to digest it. All of us 

 were dependent upon them for our daily food, for every particle 

 of food that we ate had at some time or other passed through 

 these mills, and been prepared for our use. These chlorophyll 

 mills in*>the leaf only worked by means of light. Fungi, which 

 were not manufacturing plants, could live in the dark. All 

 other green plants were hard workers, and the power they used 

 to drive their yw^re/mills sunlight. With the first rays of the 

 rising sun the mills commenced to work, and went on con- 

 tinuously until sunset. Then they had rest, and other parts of 

 the plant took up other divisions of labour— growth and cell 

 division were greatest during darkness — and thus was caused an 

 alternation of rest and work. It had been proposed to make 

 plants work night and day under electric light, and thus ripen 

 peaches and strawberries, but such long hours of work would 

 be sure to wear out their constitutions. The chlorophyll was 

 hard at work all summer gathering in and laying up supplies 



