CHAPTER XIII 



THE DISPERSAL OF SEEDS, AND A SUMMARY WITH 

 REGARD TO THE FLOWERS 



In one season a single plant, say a Foxglove, may produce 

 thousands of seeds. If every one of these seeds is to be 

 afforded an opportunity of 



developing into a mature 

 plant, means must be pro- 

 vided to enable the seeds 

 to reach suitable spots at 

 some distance from the 

 mother-plant. The seeds 

 of flowering plants are con- 

 veyed through the air in the 

 same manner as the pollen, 

 in so far that they are either 

 violently ejected {e.g. Bal- 

 sam, Oxalis), or are carried 

 by the wind {e.g. Dande- 

 lion), or borne by animals 

 {e.g. Rose, Cherry, Galium). 



Explosive fruits are not 

 common. The capsule of 

 the Violet opens into three 

 boat - shaped valves, each 

 containing a double row of 

 smoothly - polished seeds. 

 The sides of the boat-shaped 

 valves contract as they dry, 

 and fling out the seeds. To 

 understand this mechanism, 

 we have only to remember 

 the manner in which an 

 orange-pip springs out when 

 squeezed between two 

 fingers. 



Dispersal by the wind. 



i'P 



Fig. T2Q. — Right-hand figure is a vertical 

 section of infructescence of Dandelion: br— 

 involucre. Left-hand figure is a vertical sec- 

 tion of a single fruit (achene) with a pappus 

 0^) on a long beak; ^£:=pericarp ; ^f=testa 

 of^the seed; cf?^ = cotyledons ; r= radicle. 



—To facilitate dispersal by the 

 95 



