132 A NATURALIST IN THE PACIFIC chap- 



and inland floras, we have in the mangrove-formation families, 

 sub-families, and genera almost peculiar to itself, and including 

 plants, like those of the Rhizophoreae, that in their characters 

 betray but little kinship with others and give but little indication 

 of their descent. The mangroves have remained through the ages 

 as something apart from other coast-plants, isolated both in their 

 history and in their characters, and especially distinguished by 

 their " adaptations " to their surroundings. 



Such is the line of argument followed by this eminent German 

 botanist in his account of the development of a tropical strand- 

 flora. In various parts of this work I have ventured to suggest 

 that the mangroves may be the remnant of an ancient flora widely 

 distributed over the lower levels and coastal regions of the globe 

 in an age when vivipary (meaning, thereby, germination on the 

 plant) was the rule rather than the exception. At such a period, 

 as I imagine, the climatic conditions of the earth were much more 

 uniform than they are at present, at least in the lower levels ; and a 

 warm atmosphere, charged with aqueous vapour and heavy with 

 mist and cloud, enveloped a large portion of the globe. The 

 mangroves, it may be remarked, are by no means universally 

 distributed on tropical coasts in our own time. (Professor 

 Schimper describes their distribution in his Indo-nialayische 

 Strand-Flora, pp. 85, 86, and in the English edition of his 

 Plant- Geography, p. 409.) They are not found on rainless coasts 

 even when under the Line, except where there happen to be large 

 estuaries ; but where a rank and luxuriant inland flora betokens a 

 high degree of humidity, there they thrive. This is well illustrated 

 on the rainless shores of tropical Peru, a locality described in 

 Chapter XXXII. of this work. 



Yet if, as it is here contended, the mangroves form a remnant 

 of a once widely spread viviparous flora, it might be expected that 

 the beach-plants of that age would have been also viviparous, and 

 that with their present descendants, as well as with some of the 

 inland plants allied to them, we ought to find in the anomalous 

 structure of the seed some indication of the lost viviparous habit. 

 This appears to be the case, as described in Note 50, with the 

 Barringtoniae, a tribe that has supplied some of the most 

 characteristic beach-trees, and also with some genera of the 

 Guttiferae. Perhaps, indeed, when the seeds of several other 

 littoral beach-trees come to be examined, for instance, Guettarda, 

 analogous structures may be found. 



Although the beach-flora of the tropics is less stable in its 



