16 BRITISH FLOWERING PLANTS chap. 



Nightshade (Circsea), some Forget-me-nots, etc. That 

 these hooks really serve to attach the seeds to passing 

 animals is shown by the interesting fact that they are 

 characteristic of low plants. In our flora they do not 

 occur on any plant which exceeds 2 or 3 feet in height, 

 nor do they occur on water plants. 



On the other hand, this argument does not apply to 

 seeds which are eaten and thus carried by animals, 

 especially by quadrupeds and birds. To this class 

 belong all those popularly known as fruits and nuts, viz. , 

 Apple, Pear, Plum, Hazel, Beech, Oak, etc., etc. 



It is interesting that while more or less green and 

 inconspicuous when immature, in many cases as they 

 become ripe they assume bright colours, especially 

 orange, red, purple, and dark blue. It seems probable 

 that it is an advantage for fruits which ripen when the 

 leaves are still green to be red, as this gives the greatest 

 contrast. On the other hand, red would not be con- 

 spicuous against faded leaves which are brown, or even 

 sometimes themselves reddish. For such fruits, blue or 

 black would be more advantageous, and, as a matter of 

 fact, many heath and moor species have bluish or black 

 fruit, as, for instance, the Bilberry, the allied Vaccinium 

 uliginosum, or the Black Bearberry. 



In some cases the juicy pulp only is assimilated, 

 and the hard seeds pass through uninjured ; but feven 

 digestible seeds often pass undigested ; moreover, we 

 know that small birds continually fall victims to 

 hawks, etc., and perish from accidents, so that the cases 

 are numerous where undigested seeds have a chance of 

 growing. 



The northern birds, as Mr. Eeid points out,^ generally 

 come to us in autumn when the seeds are ripe, and must 

 bring many southwards with them. 



Many plants develop their seeds in capsules, which 

 open at the upper end, so that while the seeds lie 

 quiet while it is calm, they are jerked out by a high 

 wind. This is the case, for instance, in Poppies, in 



' Origin of the British Flora. 



