Longer it 1 1 of Seeds. 



407 



a lai<re one at the inner end ; the latter had protoplasmic con- 

 tents. 



The shape of the luniina trives the cells a very characteristic 

 appearance. At intervals across the luniina were delicate oblique 

 partitions of cuticularised substance. The seeds swelled after 

 about two hours in sulphuric acid at 22 deg. C. The coats of 

 the swollen seeds were very soft, and it was difficult to cut 

 satisfactory^ sections of them. So I embedded them in paraffin 

 without dehydrating, and cut sections with a horizontal micro- 

 tome. The sections showed that the palisade cells were corroded 

 away somewhat irregularly, so that it was difficult to judge to 

 what extent the corrosion was necessary in order to permit 

 water to enter, but it seems probable that it must at least pjro- 

 ceed just beyond the last cross partition in any one cell. The 

 entry of water into the cell would cause such a distortion of 

 the micellae of cellulose as to give rise internal stresses and 

 strains would disturb the micellae in other parts, so that 

 they would become forcibly separated, and this would enable 

 the molecules of water to push their way in. The results of 

 the above experiments are summarised in the following table : — 



Seed. 



Thickness of 

 Cuticle. 



Indigofera arrecta - 0.008 inni. 

 Cytisus albus - - 0.004 mm. 

 Acacia melanoxylon 0.013 mm. 

 Melilotiis alba - No true 



cuticle 

 Albizzia l(i]jliantha- 0.015 mm. 



Canuii inJica - 



No cuticle 



Averajft- time in 



sulpliuric acid at 



12-1.')"C. required 



to produce s\v. 



15-30 mill. 



15 min. 



I hr. 20 mill. - 



10 min. 



40 hrs. at 12° C. 

 7 hrs. at 30° C. 

 21u-s. 



Iniperineable portion 

 of Seed. 



Cuticle 

 Cuticle 

 Cuticle 

 Cuticularised ends of 



palisade cells 

 Cuticle and palisade 



cells 

 Palisade cells only 



Nature of Cuticle and Methods of Softening 

 Hard Seeds. 



In the formation of cuticle the cell walls have become im- 

 pregnated with cutin. Whether these materials penetrate the 

 cell wall as a waxy substance, or whether they are deposited as 

 the result of subsequent chemical change, is unknown. Van 

 Wisselingh,! contrary to the opinions of Von Hohnel and Zim- 



1 Archives Neerlandaises des Sciences Rlxactes et Naturelles, tome x.wiii., 1894. 



