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PLANT PHYSIOLOGY AXD ECOLOGY 



by the maimer of reproduction and especially by the number of 

 seeds produced. The character of the family is also affected by 

 the height and branching of the plant and by the position of the 

 seeds upon it. In the case of species whose fruits or seeds are 

 immobile, i.e.. not well adapted for migration, the seeds fall directly 

 beneath the parent. The resulting family is small and definite. 

 A similar group is often produced by offshoots when these do not 

 carrv- the new plants too far from the original one. If the fruits 

 or seeds are readily carried, i.e.. are mobile, the degree of aggre- 



FiG. 96. Simple aggregation of Cori.spermum seedlings beneath and about 



the parent plant. 



gation in the family is correspondingly decrea.sed, since the seeds 

 are carried away from the parent. Verv' mobile forms, such as 

 the dandelion, rarely produce families for this reason, and this 

 is often true also of plants which produce few seeds. Annuals 

 occur more frequently in families, owing to the large number of 

 seeds and the frequent ab.sence of de^'ices for migration. ^lany 

 perennials also arrange themselves in families. This is true of 

 immobile perennials as well as those that migrate by means of 

 underground parts. 



