The Science of Plant Growing 21 



a colourless envelope or cell wall. Each individual constitutes a com- 

 plete plant. The interior is filled with a particle of granular, jelly-like 

 matter, stained green. This jelly-like substance has been named proto- 

 plasm, and, as it is present in all living plants and animals, it is con- 

 sidered the seat of life. It is the essential part of the plant, as we shall 

 see presently. When any of the cells has reached full size, it divides 

 into two equal parts, which become separate individuals, and repeat 

 the history of their parent by feeding, growing, and again dividing. 

 Those who would see- this process must needs burn the midnight oil, 

 for one-celled green plants manufacture food from the atmosphere by 

 day in preparation for dividing by night. Rain brings down many of 

 these plants from the roof-gutters of the house, and if a drop of watei 

 from the water butt is examined in summer or other suitable time it 

 will be found to contain more or less numerous organisms, some con- 

 sisting of a particle of green jelly, without the cell wall, and larger 

 ones with an investing wall, but both sizes moving about rapidly. The 

 movement is due to the rapid vibration of two slender thread-like portions 

 of the protoplasm, without colour, and therefore invisible till something 

 is put in the water to bring the organisms to a state of rest. After 

 a time they lose these filaments, and become surrounded by a cell wall, 

 like those on the damp wall. From the damp wall, or from the water 

 in the butt, these lowly plants absorb their food, or rather the raw 

 materials from which they manufacture it. Already we can see that 

 the cell wall can be dispensed with as so much dead matter, while the 

 naked protoplasm is still termed a cell, and is equally an individual plant. 



The Yeast Plant (Saccharomyces cerevisice), such as is used by the 

 brewer, if put in any clear liquid containing suitable food (malt, for 

 instance), the liquid, if stood in a warm place for some hours, will 

 become cloudy or muddy, this being due to the rapid multiplication 

 of the Yeast Plant. The temperature of the fermenting liquid is raised 

 as a result of the chemical changes being brought about in the con- 

 stitution of the liquid by the Yeast Plant. If a drop is examined under 

 the microscope, the plant is seen to be oval, smaller than the Protococcus, 

 but without the green colouring pigment of that, showing that it belongs 

 to the great group of Fungi. It is also rapidly multiplying by budding 

 at one end. The tiny protuberance or offset grows to nearly the size of 

 its parent, and drops away as a new individual. 



The "clubbing" of turnips, cabbages, cauliflower, and other members 

 of the Crucifer family is due to another fungus, which lives within the 

 roots during summer and other mild periods, causing great swellings to 

 arise. At this period each individual multiplies rapidly, and rests 

 enclosed in a cell wall of its own during winter; but with a rise of 

 temperature in spring the protoplasm quits the cells and unites in 

 a jelly-like mass, which moves through or over damp soil in quest of 

 fresh plants to attack. 



From these three plants it will be seen that the protoplasm possesses 



