EXPLANATION OF THE DIAGRAMS ILLUSTRATING 

 THE CAUSES OF SEED-BUOYANCY 



I. Entada scandcns (natural size) : (<r), the shell ; (b), the kernel ; [c), the inter- 

 cotyledonary cavity. The shell consists of three coats — an outer and an inner 

 hard chitinous coat, and an intermediate layer of brown cellular tissue contain- 

 ing little or no air! The bu<_>yancy is due entirely to the central cavity, neither 

 the seed-tests nor the seed contents possessing any floating power (see page i8i). 



2 Miituna itreiis, from Hawaii (natural size). The kernel {b) sinks, and the shell has 

 no floating power except where it possesses (under the raphe) a layer of dark 

 brown, air-liearing, spongy tissue {a). This, how'ever, is not sufficiently developed 

 to endow the seed with buoyancy, wliich is due to the intercotyledonary cavity {c). 

 (see page ill). 



CMiiniua iiigaiitea, from Fiji (natural size). The kernel (/') sinks, and the seed owes 



3. its floating power entirely to the existence in the shell {a) of a layer of brown, 



4. I spongy, air-bearing tissue which is mostly developed at the circumference and is 

 I almost wanting at the flat sides of the seed (see page 115). 



iDioclea {vioiacea '), from P^iji (natural size). Here the kernel (^) is buoyant and 



5. ] endows the seed with floating power. Though the shell [a) possesses a thick 



6. j layer of reddish-brown cellular tissue, this tissue contains but iitile air and aids 

 \ the floating power Init slightly (see page 113). 



7. Slrougylodou iihidiiin, from Fiji (natural size). The floating power is due entirely 



to the buoyant kernel (/')• There is a very scanty amount of loose brown tissue 

 (a) under the raphe : but it has no appreciable effect on the buoyancy (see 

 page 113). 



' Cicsalpinia bondiuella and C. boiiduc, from Fiji (natural size). Neither the seed- 

 tests {a) nor the kernel (/;) have any floating power in themselves, the buoyancy 

 'i- being connected with , a large internal cavity (r), which normally is intercotyle- 



9. -( donary, as in Fig. 8 (C bonducella). With l)oth plants, but more especially 

 10. with C". bonduc (Figs. 9 and lo), there may be a lateral cavity («'), or the kernel 



may be loose in the shell (Fig. 10), Init this does not necessarily imply Imoyancy 

 \ (see page 194). 



(Arenaria peploides (enlarged : seeds 4 nun. in size). Here the curved embryo (a) 

 -[ sinks, and the spongy air-bearing alVjumen ((^) gives buoyancy to the seed (see 

 I page 116). 



II 

 12, 



13. Euphorbia paralias (enlarged : seeds 3 mm. in size). The kernel (3) sinks, and the 



seed owes its buoyancy to a layer of air-bearing tissue [a] in the shell (see 

 page 1 16). 



14. Morinda citrifoUa (enlarged pyrene 7 mm. long). The floating power is due 



to the bladder-like air cavity (a). The seed {b\ proper is enclosed in the 

 woody tissue behind the bladder (see page 1 12). 



15. Ctiiiir/iila (seed enlarged), from the \'alparaiso beach-drift (see page li5). The 



kernel (/') has no l)uoyancy. The shell (a) is formed of two layers of air-bearing 

 tissue, the outer composed of prismatic cells and the inner of a spongy vacuola- 

 material. 



