772 Journal of Agriculture. [lo Dec, 1910. 



difference in the size and sliape of the cavities in the two cases. They 

 found, however, that outside the palisade cells of the hard seeds of 

 /. arrecta was a thin membrane through which ^vater could not penetrate 

 but, probably owing to a defective stain, they were unable to determine 

 the exact nature of this membrane. 



In 1908, Dr. White^ made a further examination of these seeds and 

 of a large number of other hard seeds and found that the membrane was 

 composed of a material known as cuticle, which is impermeable 

 to water, and further, that a similar membrane was present on 

 each seed she examined. The presence of the cuticle is detected by 

 using certain stains which colour the cuticle in a characteristic manner. 

 The stain used in this case was chloro-zinc-iodine, which colours cuticle 

 dark-brown, the soft cell-walls blue or magenta and the living cell con- 

 tents a lighter brown. Fig. c of the plate shows a small portion of the 

 seed coat of the Blackwood {Acacia melanoxylon) stained in this way and 

 the extreme thickness of the cuticle can be clearly seen. The cuticular 

 material is not always confined to the outer membrane, but may be laid 

 down also in the walls of the palisade cells and in some cases, the whole 

 cell-wall may become cuticularised in this way. An instance of this is 

 found in the seed of the Bottle-brush Wattle {Albizzia lophantha). In 

 Fig. f there is a double row of palisade cells, the outer row being entirely 

 cuticularised and the inner only partially. Seeds of this type are natur- 

 ally more resistant than those in which the cuticularisation is confined to 

 the outer membrane. Of all the hard seeds examined by Dr. White and 

 myself, in one case only, the Canna, was there no well defined cuticle 

 outside the palisade cells, and it is evident that this seed must owe its 

 impermeability entirely to the cuticularised walls of these cells. 



As to the nature of cuticle, it is believed to be formed by the laying 

 down of particles of w\axy or fatty substance in the already-existing cell- 

 wall. A cuticle consists therefore of the original cell-wall, which is made 

 up of cellulose or some sim.ilar material, permeated through and through 

 with oarticles of wax. Such a membrane would differ from unchanged 

 cellul(xse just as a sheet of waxed or oiled paper differs from one of 

 blotting paper ; water would be held by the former but would pass readily 

 through the latter, and the more complete the impregnation with wax the 

 greater would be the resistance to the passage of the water. 



EXPLANATION OF PLATE. 

 [a). Seed coat of Indigofera arrecta after trealment with chloroform. 

 \b). Similar preparation of Cytisus atbus. 

 (c). Untreated seed coat of Blackwood. 

 \d). Same after treatment with sulphuric acid. 

 \e). Seed coat of Melilot after chloroform treatment. 

 (/). Untreated seed coat of Bottle-brush Wattle. 

 \g). Same tested after four months soaking in chloroform. 

 (/?). Seed coat of Canna tested after treatment with chloroform. 



(All the preparations after testing with chloro-zinc-iodine.) 



We have now to consider the various methods by which it is possible 

 to render hard .seeds permeable to water. There are several ways by 

 which this can be done, one is to scratch or remove the outer cuticle, 

 while another is to extract the waxy material from it by means of certain 

 chemicals or to subject it to the action of hot water, the former method 

 is the most practical and is more comm.only employed in the case of very 



4. Proc Boy Soc. Vict., Vol. XXI, I'L 1. 



