346 'LAW OF LOSS ' [CH. 



Angiosperms. It might well have been expected that when 

 certain Angiosperms adopted water-life so completely as even 

 to revert to the remotely ancestral habit of submerged fertili- 

 sation, they would also simultaneously revert to ciliated sperms, 

 associated with a broad stylar canal and open micropyle. Such 

 a trumpet-shaped stigma as that possessed by Zannichellta 

 seems, indeed, exactly adapted for the entry of swimming 

 sperms. But no such ciliated Angiospermic gametes have come 

 into existence; those Flowering Plants which are pollinated 

 beneath the water, go through all the processes of making 

 pollen-grains as for aerial pollination, with such slight modifica- 

 tions as will permit them to be carried passively to the stigma 

 by gravity or water currents. It seems that cilia once lost 

 cannot be recovered, even when the circumstances in which 

 they were formerly of use again recur, and the plant has, as it 

 were, to patch up some substitute. 



If the Law of Loss be accepted as of general application, 

 it furnishes a clue to certain phylogenetic problems. We have 

 already alluded to the light which it throws on the difficult 

 question of the interpretation of the flower of Naias 1 . Again it 

 is highly unlikely, on the Law of Loss, that a naked unisexual 

 flower could evolve into a hermaphrodite flower with a peri- 

 anth, and hence the law points to the primitiveness of such 

 floral types as those found among the Ranales and Alismaceae. 



We have already 2 considered Dr Scott's suggestion that the 

 anatomical peculiarities of the polystelic genus Gunnera might 

 lie in an ancestral history in which an original terrestrial period, 

 followed by an aquatic phase, has been succeeded by a second 

 terrestrial period. Expressing this example in terms of the 

 Law of Loss, we may say that the cambial system, once dis- 

 carded under the influence of water-life, could not be regained 

 even when the plant reverted to terrestrial conditions; the 

 expedient of adding to the number of the existing reduced steles 

 represents a device for repairing this irrevocable loss of means 

 by such substitutes as are to hand. 



1 See p. 315. 2 See p. 180. 



