470 A NATURALIST IN THE PACIFIC chap. 



of plants living in drier stations. After this come those mangroves, 

 where, as in Avicennia, germination is completed on the tree or 

 shrub, but the seedling at once liberates itself from the parent. 

 Last of all there is the stage of the typical mangroves, Rhizophora 

 and Bruguiera, where the seedling remains for months growing on 

 the tree and hangs from the branches. 



Vivipary, as above stated, presents itself as a matter of small 

 beginnings. My own view, however, is that it is a matter of small 

 "endings" ; and that if we were to commence the scale not with 

 the immature seed lying on the soil, but with the seedling sus- 

 pended from the branches of a Rhizophora tree, we should record 

 the various epochs in the history of vivipary throughout the plant- 

 world. From this standpoint the occasional cases of incomplete 

 vivipary displayed outside the mangrove-swamp represent a lost 

 habit belonging to a primeval period when the climatic conditions 

 were uniform over most of the earth, an age almost of eternal 

 gloom, when the air was ever saturated with aqueous vapour, and 

 when the sun's rays were screened off by a dense cloud-covering 

 that enveloped the globe, an age of which the existing mangrove 

 swamps alone afford an imperfect indication. Yet even now we 

 can say with Schimper that " dense and frequently repeated 

 cloudiness apparently represents the most essential climatic 

 condition for the occurrence of mangrove in the tropics " {Plant 

 Geography, p. 409). 



But, to return to the subject immediately under consideration, 

 if my view is correct we ought to find indications of the lost habit 

 in the anomalous structure of the seeds of some inland plants ; and, 

 indeed, it is shown in Note 50 that this view can be taken of the 

 singular structure of the seeds of the Myrtaceous genera, Barring- 

 tonia and Careya, and of the genera of some other orders, and can 

 be extended by implication to several other plants possessing 

 similar seed-structures. 



With regard to the subject generally, it may be remarked that 

 although normal vivipary is mainly restricted to the plants of a 

 mangrove swamp, by no means all mangrove plants are typically 

 viviparous. This habit in its most complex form is exhibited as a 

 rule by plants with firm, somewhat fleshy, usually one-seeded, 

 indehiscent fruits, such as we find with Rhizophora and Bruguiera ; 

 but plants with follicular fruits, such as occur with vEgiceras, may 

 also display it in a fashion nearly as complex. Generally speaking, 

 however, plants with hard, dry fruits, such as are owned by 

 Excaecaria, Heritiera, and Lumnitzera, are non-viviparous, though 



