xii CAUSES OF BUOYANCY OF SEEDS AND FRUITS 107 



SECTION IV. The floating power is derived from empty 

 seed-cavities, where owing to abortion of the ovule 

 or some similar cause the seed is not developed. 

 S. G. Morinda citrifolia. 

 G. Premna tahitensis. 



Note. — Professor Schimper, in the case of Morinda citrifolia, 

 holds the view that we have here a special adaptation to dispersal 

 by currents. 



SECOND GROUP. — Here the floating power is due mainly or 

 entirely to buoyant kernels. In the case of seeds the 

 tests are non-buoyant; but with "stones" the floating 

 capacity may be aided by a layer of air-bearing tissue 

 inside the shell. 



SECTION I. Non-Leguminous. 



S. G. Ximenia americana (drupe). 



S. G. Calophyllum inophyllum (drupe). 



Note. — Professor Schimper would place these two plants in the 

 second section of the third group on account of the layer of air- 

 bearing tissue inside the shell of the " stone " ; but they are 

 assigned to this section, since the floating power is mainly due to 

 the buoyant kernel. 



Arenaria (Honckeneya) peploides, a British beach plant, belongs 

 here. 



SECTION II. Leguminous seeds. 

 G. Dioclea. 



G. Strongylodon lucidum. 

 S. Canavalia (generic). 

 G. Canavalia sericea. 

 S. G. Canavalia obtusifolia. 



S. Erythrina (generic). 

 S. G. Erythrina indica. 



P. Erythrina ovalifolia (Penzigj. 

 S. G. Sophora tomentosa. 

 G. Afzelia bijuga. 

 G. Lathyrus ? 



THIRD GROUP. — The floating power is due to the presence 

 of air-bearing tissue in the seed-tests or fruit-coats. 



