xxvi DIANELLA 



357 



often pretty blue berries, that extends over tropical Africa, tro- 

 pical Asia, the Mascarene Islands, Malaya, Australia, and New 

 Zealand, and is found in all the larger Pacific archipelagoes. 

 Of the twelve species named in the Index Kewensis only two 

 belong to America, occurring respectively in Cuba and Vene- 

 zuela. There are two species in the islands of the tropical Pacific : 

 {a) Dianella ensifolia, found in Hawaii and ranging over the 

 Mascarene Islands, India, China, Malaya, and tropical Australia ; 

 and (b) D. intermedia, recorded from most of the groups of the 

 South Pacific (Fiji, Tonga, Rarotonga, Tahiti), and occurring also 

 in Norfolk Island and New Zealand. These two plants occur in 

 similar stations all over Polynesia, sometimes growing in the grassy 

 plains on the dry side of an island, at other times extending up 

 the thinly wooded mountain slopes and reaching the hill-crests 

 some 2,000 or 3,000 feet above the sea. Their berries would readily 

 attract birds ; and their seeds, about one-fifth of an inch (5 mm.) 

 in size in the case of D. ensifolia, could be carried uninjured in the 

 stomach and intestines of a bird. 



Summary. 



(1) A later period in the era of the general dispersal of 

 Malayan plants over the Pacific is indicated by the genera 

 that contain species found outside each group as well as species 

 restricted to it. 



(2) In this period the extremely variable or polymorphous 

 species plays a conspicuous part, as represented in such genera as 

 Alphitonia, Dodonaea, Metrosideros, Pisonia, and Wikstrcemia. 



(3) The first stage is displayed by a solitary widely-ranging 

 species found over most of the Polynesian archipelagoes, and vary- 

 ing independently in every group. 



(4) The next stage is shown where the polymorphous species, 

 having done its work of distributing the genus, ceases to wander 

 and settles down and " differentiates " in all the groups ; and the 

 genus thus includes both peculiar and widely-ranging species in each 

 group. Most of the genera possessing polymorphous species are in 

 this stage. 



(5) The following stage is displayed by those genera like 

 Elaeocarpus, Eugenia, and Peperomia, where peculiar species are 

 especially developed in particular groups, and we get subcentres 

 of distribution for the genus, that is to say, small gatherings of 



