

1907] How THE Seeds of Plants are Spread \/i/29ZL V^ 



In a number of these plants the seed-capsules split at the top 

 and form a toothed edge. The night-flowering catchfly and 

 other members of the allied genera, Silene and Lychnis, are ex- 

 amples of this class. The teeth, although in appearance looking 

 as if the}' were merely the result of the top splitting ojjen to let 

 out the seeds, in reality also answer quite another purpose, 

 namely, to scatter the seeds as they are shaken out, so that they 

 may not fall too closely together. A rather more complicated 

 example to gain the same end is shown in the seed pod or capsule 

 of the common garden poppy. Here there is a cap to prevent 

 the seeds from being shaken out too fast, and small holes round 

 the sides just below the cap. In fact, it is a natural sifter from 

 which the seeds are shaken out a few at a time, usually by the 

 wind. Indeed the only method whereby the seeds can get out 

 is by the plant being shaken or broken down, and this latter 

 alternative would be only accidental and therefore does not 

 need to be taken into consideration here. 



There are a great many other modifications of this group 

 which will suggest themselves to the observant student. A large 

 number of seeds are, however, scattered by the w^ind that are 

 only partly modified for the purpose, and with some plants it is 

 difficult to tell whether they are in any way adapted for that 

 special purpose. 



IV. Seeds that are Spread by Clinging and Sticking. 



Seeds of this group depend principally upon mammals for 

 their distribution. They contain among their best known forms 

 those seeds which are commonly called 'burs,' though several 

 grasses are also included in the group. 



'Burs' are known to most people, especially to owners of 

 thick haired dogs. Yet how few consider why they cling to al- 

 most any thing that comes in contact with them ! 



To a Nature student the reason is at once apparent. They 

 have become adapted to clinging so that they may be carried 

 to new localities and so become spread by degrees over wide 

 areas. 



Examples of this class of seeds or seed pods will be found 

 everywhere. The different blue-burs, cockle-burs, bur marigolds 

 and wild liquorice (Glycyrrhiza) are common examples, but there 

 are many more, some consisting of a single seed, while in others 

 the whole pod with several seeds is carried. 



A different method of distribution is found in seeds which 



