42 BRITISH FLOWERING PLANTS chap. 



minimum, and soon increasing again and attaining a 

 maximum, after which it tapers to the summit. This 

 conforms to the ideal proportions of a pillar of uniform 

 resistance. 



These considerations, then, seem to throw, at any 

 rate, some light on the different forms assumed by the 

 stems of plants. They may seem obvious, but excepting, 

 indeed, as regards the round and compressed forms, I do 

 not find them stated in botanical works, and, indeed, I 

 was myself for a time in some doubt on the subject. 

 Thus, then, we see that plants adopted for themselves, 

 thousands and indeed millions of years ago, principles 

 of construction, adapted to secure the greatest strength 

 with the least expenditure of materials, which have been 

 gradually worked out and applied to our buildings by 

 the skill and science of our architects and engineers. 



The Sense Organs of Plants 



We all remember the old aphorism of Linnaeus : 

 "Stones grow; plants grow and live; animals grow, 

 live, and feel." Plants, however, feel, though there is 

 no reason to suppose that they can enjoy or suffer. 

 The movements of plants, especially the " sleep " of 

 flowers and leaves, which haA^e been already referred to, 

 and the eircumnutation of climbing plants — all such 

 movements imply sensitiveness. 



It may seem at first sight somewhat far-fetched to 

 speak of the sensitive organs of plants. We cannot, 

 of course, attribute consciousness to them, but the 

 mechanism which originates and produces movement 

 presents remarkable analogies and similarities in the 

 two kingdoms. As in animals so also in plants, we find 

 papillae or processes which localise, and thus enhance, 

 the pressure on limited portions of the protoplasm. 

 Any one who has ever suffered from the elevation of a 

 papilla, or a few papillae, on the skin, will realise the 

 effect produced by confining the pressure, which is 

 generally spread over a comparatively large surface, to 

 a limited area. Again, the transmission of impressions 



