THE GENERAL SHAPES OF PLANTS. 141 



were they not important items in the argument. More 

 instructive perhaps, because less familiar, is the fact that we 

 miss this extreme contrast in flowering plants which have not 

 their higher and lower portions exposed to conditions thus 

 extremely contrasted. A parasite like the Dodder, growing 

 in entangled masses upon other plants, from which it sucks 

 the juices, is not thus divisible into two strongly-distinguished 

 halves. 



Leaving out of consideration the difference between the 

 supporting part and the supported part in phamogams, and 

 looking at the supported part only, we observe between its 

 form and the habitual incidence of forces, a relation like that 

 which we observed in the simpler plants. Phsenogams that 

 are practically if not literally uniaxial, and those which de- 

 velop their lateral axes only in the shape of axillary flowers, 

 when uninterfered with commonly send up vertical stems 

 round which the leaves and flowers are disposed with a more 

 or less decided radial symmetry. Gardens and fields supply 

 us with such instances as the Tulip and the Orchis; and, on 

 a larger scale, the Palms and the Aloes are fertile in ex- 

 amples. The exceptions, too, are instructive. Besides the 

 individual divergences arising from special interferences, there 

 are to be traced general divergences where the habits of the 

 plants expose them to general interferences in anything 

 approaching to constant ways. Plants which, like the Fox- 

 glove, have spikes of flowers that are borne on flexible foot- 

 stalks, have their flowers habitually bent round to one face of 

 the stem: an unlikeness of distribution probably caused by 

 unlikeness in the relation to the Sun's rays. The wild Hya- 

 cinth, too, with stem so flexible that its upper part droops, 

 shows us how a consequent difference in the action of gravity 

 on the flowers, causes them to deviate from their typically- 

 radial arrangement towards a bilateral arrangement. 



Much more conspicuous are these general and special rela- 

 tions of form to general and special actions in the environ- 

 ment, among phasnogams that are multiaxial. That when 



