DIVISION OF INDIVIDUALS 309 



nection it is to be said that many plants, especially fungi, produce 

 bodies termed spores that are multicellular. 



Sexual reproduction is the method by which two masses of 

 protoplasm, gametes, of unlike physiological character and gen- 

 erally showing morphological distinctions, are fused to form a 

 single cell, or spore, capable of giving rise to a new individual. 

 The gametes are usually directed to each other by chemotaxis, 

 and the mechanism of their union is most diverse in various spe- 

 cies. Neither of the gametes are usually capable of developing 

 into an individual alone. The union of two gametes in sexual re- 

 production brings together the multi-complex inherited qualities 

 of two parents with their similarly multi-complex ancestry, and 

 tends to obliterate the isolated variations shown by either parent. 



The organs concerned in both asexual and sexual formation 

 of spores generally show such highly differentiated morpholog- 

 ical structure, and diversity of development that the study of 

 their activity constitutes a separate branch of the subject, and 

 lies beyond the limits of this volume. The following discussions 

 and experiments will therefore deal only with the forms of asex- 

 ual reproduction which might be included in somatic processes, 

 with one or two examples of the factors operative in calling out 

 the activities of other mechanisms. 



395. Multiplication of Individuals as a Result of Senescence 

 and Death of a Part of the Body of the Plant. The simplest 

 manner in which new individuals may arise among the higher 

 plants is that by which the older parfs of the main axis die 

 away, and the separated members continue their growth, replac- 

 ing the organs of which they have been deprived by the death of 

 the older member. The separated portions may or may not take 

 on special form or structure, a matter dependent upon the sea- 

 sonal conditions which they must endure. 



396. Division of Individuals in Marchantia, Azolla, Marsilea, 

 and Lycopodium. Cultivate a number of specimens of the plants 

 named, and note that the death of the older portions separates 

 the branches, and that these in turn subdivide and multiply the 



