32 A NATURALIST IN THE PACIFIC chap. 



buoyancy of fruit or seed cannot determine a station on a sea- 

 beach, and that some other factor makes the choice. The nature 

 of this factor I will now endeavour to explain ; but in so doing 

 it will be necessary to employ a few technical terms, which it is 

 not easy to dispense with altogether. 



It may be doubted whether Professor Schimper could have 

 conferred a greater benefit on the student of plant-distribution 

 than in his clear delineation of the connection between the habit 

 or organisation of a plant and its station. Nature has imposed an 

 important structural distinction between plants that have been 

 endowed with the means of checking excessive transpiration or 

 water-loss in stations where there is risk of drought, as in deserts 

 and in similar arid localities, and those that live in stations where 

 such safeguards are not needed. Hence arises the distinction 

 between Xerophytes on the one hand, and Hygrophytes on the 

 other. This contrast is shown not only in minute structural 

 features, but also, as my readers are aware, in the external 

 characters, as in hairiness, succulency, a leathery cuticle, the 

 occurrence of thorns, and in several other characters of the 

 plants of the steppe and the desert. This important subject is 

 dealt with by Professor Schimper in his recent work on Plant- 

 Geography ; but it was from his earlier work on the Indo- 

 Malayan strand-flora that I learned this valuable lesson in 

 plant-distribution. 



It has been ascertained, however, that a safeguard against 

 excessiv-e water-loss by transpiration is not only needed by plants 

 living in arid localities, but also by those placed at the coast. Both 

 the shore plant and the plant of the steppe and the desert present the 

 same xerophilous organisation, provision against excessive transpira- 

 tion being also required by the beach plant to prevent the injury of 

 the green cells from the accumulation of salt in the tissues. It would 

 thus appear that plants of the Hygrophytes that possess buoyant 

 seeds or fruits are gathered at the borders of ponds and rivers, whilst 

 those of the Xerophytes that are similarly endowed find their 

 station on the sea-shore. This important distinction penetrates 

 very deeply into the conditions defining the stations of plants. 

 The connection between the plant of the coast and the plant of the 

 steppe or the desert is strikingly shown on those occasions when 

 the beach plants extend inland over parched and arid plains, such 

 as occurs for instance in North Africa, and in the larger islands of 

 Fiji, as described in Chapter V. 



The causes of the buoyancy of fruits and seeds, as pointed out 



