50 



of rivers up to the point where the influence of the tide becomes 

 perceptible. Its fruits lack a pappus; the pericarp is developed into 

 a floating tissue 1); in a 3 % solution of NaCl they remained floating 

 for more than 20 weeks. They are chiefly dispersed by water; by 

 wind they might in bare localities be driven forth a few meters but 

 on account of their weight they are unfit for a somewhat prolonged 

 flight through the air. It is quite impossible that they have crossed 

 over to Krakatao from some of the neigbouring islands ,,auf den 

 Fliigeln des Windes" as Penzig 2 ) has it. 



If Treub has really found this plant ,,sur la montagne proprement 

 dite" and not at a short distance from the beach in a low-lying 

 ravine opening on the coast, with perhaps a saline soil 3 ), it can have 

 occurred only in a few specimens gone astray from the shore. This 

 species cannot possibly have taken an important part in the vegeta- 

 tion of the higher interior parts. 



2 and 3. Two species of Conyza. 



The genus Conyza, as delimited by Hoffmann in Engler und 

 Prantl (Natiirl. Pflanzenfamilien IV, pars 5, 169) is in the Dutch 

 Fast Indies only represented by a few species in the mountainous 

 districts above 1000 m. Treub cannot have found these on the 

 lower parts of Krakatao. But in the only flora of the Dutch Indies 

 I r e u b had at his disposal (Miquel, Flora Ind. Bat. II, 40) Conyza 

 includes also the present genera P/uchea and B/umea, whilst a 

 species of Erigeron so closely resembles Conyza that it is often 

 wrongly determined as such. In these 3 genera we have to look 

 for T r e u b's species of Conyza. 



Pluchea is in the Dutch Indies represented only by PI. indica 

 /.ess. (- Conyza indica Miq.). This is a halo-xerophilous shrub of 

 sunny or slightly shadowed, periodically very dry and frequently saline 

 localities, chiefly occurring on the heavier soils and in stony or 

 calcareous localities either near the sea or rather far from it; it is also 

 found around salt-water springs. It is not at all a beach plant, though 

 sometimes recorded as such. In the interior it is often cultivated in 



^) Cf. Sc lii in per, Indo-Malayische Strandflora (1891), p. 172, under the name of 

 Wollastonia glabra; p. 157, under tlie name of Wedelia biflora. 



2 ) Cf. Penzig in Ann. |a.d. Bot- Buitenzorg XVIII (1902) p. 109. 



3 ) Verbeek, Krakatau, Dutch Edition (1888), p. 302 (translated): ,,The eruptive 

 .products impregnated with sea-water were (in Oct. 1883) in the lower layers still very 

 ,liot; the sea-water and especially the rain-water oozed through the porous pumice-sand, 

 , carried the dissolved salts of the sea-water downwards and deposited them as a white 

 ,or gray salt-crust in the localities were the hot water could escape". The eruptive 



.products contained according to Verbeek (Krakatau. Dutch Edition (1888), p. 292 

 analyses 7, 8, 9)) 0,05-1.00% salt. 



