28 Expedition of 1906 



Sea or from the different localities which we visited on the coasts of 

 Java and Sumatra. They all belong to strand-plants which are not 

 confined to the coasts of Java and Sumatra and the numerous islands 

 in the Java Sea or to the Malay Archipelago, but are widely dis- 

 tributed from Africa to New Guinea, some species being met with 

 throughout the whole of the tropics. It is these plants which 

 constitute the first colonists of recently formed coral reefs and 

 islands. They owe their lightness and buoyancy to air-spaces in the 

 pericarp and testa or to the abundance of light floating tissue, while 

 a hard and impervious inner coat affords protection to the embryo 

 against the injurious effects of sea- water. It is by virtue of these 

 features that the seeds and fruits of strand-plants are widely distri- 

 buted and act as the pioneers of vegetation on land recently raised 

 above sea-level. 



The species which we found in the new strand-flora of Krakatau 

 are typical strand-plants. Within the Drift-zone we came to a low 

 carpet of a tropical dune-flora, the Pes-caprae formation, as it has 

 been called by Schimper, forming a zone in front of the forest-belt 

 which varies in breadth according to the nature of the ground. We had 

 previously met with the most striking and important representatives 

 of this formation on the sandy littoral of Edam. Here, as in Edam, 

 the runners of Spinifex squarrosus and the long trailing shoots of 

 Ipotnaea Pes-caprae 1 rooted at the nodes and bearing large funnel- 

 shaped flowers of a blue-violet colour and thick fleshy leaves form 

 a network on the loose substratum. With these are associated shoots 

 of some Leguminous species clinging close to the ground, the yellow- 

 flowering Vigna Intea and Vigna lutcola and the large-leaved 

 Canavalia obtusifolia. Here and there tall grasses and Cyperaceae 

 rise above the regular network of creeping steins, a spurge, charac- 

 terised by waxy glaucous leaves and low bushes becoming taller and 

 more abundant as we approached the forest-belt. We found several 

 old acquaintances from Edam and Vlakke Hoek, the widely spread 

 Malvaceous species, Hibiscus tiliaceus, with its beautiful yellow 

 flowers, also Scacvola Koeuigii, Clerodeudrou inerme, and Premna 

 foetida ; a thick felt of the yellowish- green cylindrical threads of 

 CassytJm filiformis, assuming a brown-red colour in sunny places, 

 covered the grasses, herbaceous plants and bushes as well as the 

 branches of the taller shrubs and trees of the neighbouring strand- 

 forest (Plate V., fig. 6; PL VI., fig. 7). 



The young strand-forest of Krakatau which stretches beyond the 

 low zone of the Pes-caprae formation, and is still characterised by 



[ x Compare an account of the Flora of the Ceylon littoral by A. G. Taasley and 

 F. E. Fritsch published in the New Phytdogist, Vol. iv. p. 1, 1905.] 



