248 APPLIED BIOLOGY 



Placed in water and light the contents divide into four, eight, 

 or sixteen masses, the cell-wall breaks, and each one of these 

 masses becomes a motile stage, having the appearance shown in 

 Fig. 75, A. The two whip-like structures (flagella) have 

 lashing movements which propel the organism. The color in 

 this stage may be red, green, or a mixture of the two colors. 

 Carbohydrates are made from carbon dioxide absorbed from 

 the water. The organism also absorbs nitrogen compounds 



and other necessary elements from 

 the water, forms new protoplasm, 

 and soon grows to full size. After 

 a time the flagella are retracted; 

 f the plant enters the resting stage ; 

 FIG. 75. Sphserella. ^.motile and when conditions are favorable, 

 stage; / flagella B four tne protoplasmic contents divide 



like A inside cell-wall, formed . . , / 



by division of a non-motile again into four or more masses, 

 form similar to Fig. 74 a. c, which form the swimming stage. 



division into numerous mi j. j.* 



small cells like D. E, con- There are numerous interesting 

 jugation of two like D, form- details of structure and life-history, 



(FromStras- but thege must be j eft f()r specia l 



courses in botany. For our present 

 purposes the important facts are that Sphserella is (1) a one- 

 celled (unicellular) plant ; (2) it reproduces by a process of 

 cell-division; (3) it is able to make its own carbohydrate 

 foods from carbon dioxide and water by the action of light 

 on the protoplasm'containing coloring matter which acts like 

 chlorophyll; and (4), most remarkable of all, it swims in an 

 animal fashion in one stage of its existence. 



Plant or Animal ? We classify Sphserella as a plant be- 

 cause its nutrition is the same as that of higher green plants. 

 No known animal can make carbohydrate foods from car- 

 bon dioxide and water. The one thing about Sphserella 

 which suggests that it is an animal is that it swims ; but we 

 have already noted that reproductive cells of ferns and mosses 

 can swim, and that many higher plants have movements. 



