BOTANIZING WITH THE OKINAWANS — WALKER 379 



zone already mentioned, appearing to supply solely the limited local 

 needs, especially materials for thatching houses and weaving baskets. 

 Only on the island of Yonaguni were they found growing commercial- 

 ly, an extensive plantation there covering a large area on the side of 

 a ridge, whence they are exported. The paucity of domestic animals 

 in Okinawa seemed out of harmony with the apparent potentiality 

 for grazing. Perhaps this is a temporary postwar condition, related 

 also to the shortage of fencing materials. But there seem to be plenty 

 of forage grasses, only awaiting further agronomical study to initiate 

 their beneficial use, though of course they are soil binders wherever 

 they grow. It was noticeable after the war that the weedy grass 

 Echinochloa invaded the uncultivated ricefields in great quantity and 

 would have furnished food for domestic animals had any been left to 

 eat it. 



Kef erences have already been made to the vegetation of the southern 

 islands in connection with the account of our collecting activities. 

 The vegetation there is largely the same as on Okinawa, with but 

 minor variations. The agriculture differs a little. For example, 

 though both rice and sweetpotatoes are grown on Yonaguni Island, 

 the purposes are different. The people are said to eat the rice and 

 feed the sweetpotatoes to the pigs, whereas on Iriomote they are said to 

 eat the sweetpotatoes and export the rice for needed cash. In Yona- 

 guni we saw much grazing, especially above certain sea cliffs. The 

 animals — cattle, horses, and goats — are confined by thorny hedges of 

 Pandanus, American agave, and other plants with repelling spines. 



On Iriomote we found many mangrove swamps along the margins 

 of the estuaries (pi. 10, upper). These reach out into the water and 

 by their impeding roots cause the silt to settle. On the landward 

 side of these mangrove swamps may come Pandanus and other plants. 

 These further stabilize and build up alluvial flats at the heads and 

 margins of these estuaries. Then man clears the forest and grows 

 rice and other crops. From our headquarters in Shira-hama each 

 morning we watched the people paddle in narrow canoes or row in 

 larger boats upstream to till their fields and return at night with their 

 harvest. One mangrove swamp we visited was the sandy bottom of 

 a stream flowing into the sea. There we found, besides the mangrove 

 plants already mentioned, the characteristic shrub Avicennia marina 

 (Verbenaceae) (pi. 10, lower) sending out long underground stems 

 from which arise fingerlike aerial breathing roots, reminiscent of the 

 cypress knees of our southern swamps. There were also a semiclimb- 

 ing vine in low dense clumps, Dalbergia candenatensis (Leguminosae) , 

 the mangrove fern Acrostichum aureum, and the medium-sized, 

 widespread, more or less poisonous tree Excoecaria agallocha (Euphor- 

 biaceae) . Our most exciting mangrove discovery, however, was the 



