38 Elementary Biology. 



part of the cell is all that is required to form the basis of 

 a new individual. In the higher organisms, where cells are 

 specialised and differentiated, there are certain cells whose 

 sole function in the organism it is to produce other cells 

 capable, under certain conditions, of undergoing develop- 

 ment and growth, and of forming ultimately a new organism. 

 In the lower organisms reproduction takes place just 

 previous to death, and consists, so to speak, in the saving 

 of the last remains of the store of potential energy of the 

 parent organism. 



SECTION IV. PHYSIOLOGICAL SIGNIFICANCE OF CHLORO- 

 PHYLL. 



Hitherto we have spoken of protoplasm in general, 

 but it will have been noted that throughout reference was 

 made to the existence of two varieties of that substance 

 animal protoplasm and vegetal protoplasm. So far as the 

 morphology of protoplasm itself is concerned, the details of 

 difference between the two forms will be more easily under- 

 stood after examples of the animal and vegetal worlds have 

 been examined. At present it behoves us to notice more 

 especially the peculiarities of a substance which is present 

 in by far the majority of plants, and which is characteristic 

 in great measure of vegetal protoplasm. That substance is 

 chlorophyll, to the presence of which in certain cells the 

 familiar green colour of most plants is due. Chlorophyll 

 (save in a few rare cases) is not found uniformly diffused 

 through the protoplasm, but in the form of rounded or (more 

 rarely) of stellate or ribbon-shaped masses, lying imbedded 

 in the protoplasm. These are known technically as chloro- 

 phyll bodies. Chlorophyll bodies consist of a green pigment, 

 chlorophyll itself, united in certain definite proportions with 

 definite masses of protoplasm. The chlorophyll itself is 

 small in amount and can be extracted from the protoplasm 

 by alcohol, ether, and several other allied substances. The 



