34 



Sesbania aculeata . at least one species each of 

 Sonneratia and Desmanthus and several species each 

 of Avicennia, Laguncularia, Rhizophora and Jussiaea 

 (in addition to thB two above notedQ. This makes per- 

 haps 25 species as compared with at least several hune 

 dreds of knowh species of swamp plants. It is obvious 

 that the evidence from pneumatophores means little 

 with regard to the question of root respiration in gen- 

 eral. 



Conclusions regarding soil aeration are fre- 

 quently drawn, also, from the tendency of the roots of 

 many plants to remain in the superficial layers of 



1. Scott,- Ann. Bot. 1: 306 (1886); Goebel,- 

 Organographie, vol. 2_, p. 481 (1901). 



2. G-oebel,- Ber. deut. bot. G-es. 4: 1 (1886). 



3. Rosanoff,- Bot. Ztg. : (1891). 



4. Schenck,- Jahrb. wiss. Bot. 20: 534 (1889); 

 Flora : 83 (1889). 



5. Scenck,- loc . cit . ; Goebel- Organographie, 

 vol. 2, p. 481 (1901). 



6. Goebel,- PflanzenbioiL. Schilderungen, vol. 

 2, pp. 257-260 (1893), Organographie, vol. 2, p. 481 

 (1901). 



