190 PHYSIOLOGY 



Assimilation. — The assimilation of plants involves the 

 transformation of water and carbon dioxide into starch, 

 the use of starch, oil, mineral substances in forming pro- 

 toplasm, the disintegration of protoplasm, the giving 

 off of waste in the form of water and carbon dioxide, and 

 the passage of these products throughout the plant. If 

 a branch bearing leaves is enclosed in an air-tight jar 

 the water that is given off may be caught on the sides 

 of the jar. If a branch is enclosed with a dish of lime 

 water the carbon dioxide given off in the process of 

 breathing will turn the lime water milky. Oxygen given 

 off in the formation of starch may be caught by inserting 

 a funnel over a mass of water plants exposed to the 

 sunlight. 



Reproduction. — Eeproduction is both sexual and non- 

 sexual, as it is in animals. In non-sexual reproduction, 

 fission, budding, growth from cuttings take place ; while 

 in sexual reproduction two dissimilar cells unite and the 

 new cell divides and differentiates until a new organ- 

 ism is formed. There is a most remarkable connection 

 between the sexual and non-sexual methods of repro- 

 duction, not unlike the alternation of generations found 

 in the jellyfish, where a non-sexual generation produces 

 a sexual generation and the sexual generation in turn 

 produces a non-sexual generation. In plants, however, 

 this is not a more or less isolated case. It progresses 

 steadily from low flowerless plants to the flowering 

 forms. At first the sexual generation is prominent and 

 the non-sexual generation very insignificant as in the 

 liverworts. Later, by a series of gentle gradations, 

 the non-sexual generation becomes prominent and 



