408 Bertha Mee.^ : 



merman, concluded that cutin must always pass through cellu- 

 lose to reach cuticle. In this it differs from cork in which the 

 suberin is formed in direct contact with the protoplasm. The 

 most important impregnating substances are compounds of 

 glycerine with stearic, palmitic and suberic acids, and these, 

 being of a fatty nature, should be soluble in ordinary fat sol- 

 vents, saponified by potash, and should have a definite melting 

 point. Associated with these fatty substances are other non- 

 melting materials, and so intinuite is the connection between 

 the two that it is often difficult for the various reagents to act 

 on one of the two impregnating substances, as its action may 

 be hindered by the presence of the other. For example, a tem- 

 perature of over 200 deg. C. may be required to cause physical 

 decomposition of cutin, but once the materials are separated 

 they will remain liquid at a much lower temperature. Possibly 

 the cutin substances exist in the intact cuticle in a kind of 

 loose chemical combination. 



The work hitherto has been done with leaves of Oleander, 

 Eucalyptus, Holly, etc., in which the cuticle, though well deve- 

 loped, cannot compare for thickness with that present on the 

 outside of many hard seeds. Van Wisselingh in his work dis- 

 tinguishes between cuticle and thickened cuticularised cell walls. 

 In the former he found only a trace of cellulose or none at all, 

 while the cuticularised walls had a definite framework of cellu- 

 lose. The cuticle in these leaves would seem therefore to be 

 an exudation from the cells of the epidermis or a deposition of 

 cuticular substances on the outside of the cell walls of such cells. 

 It seems, however, highly improbable that a cuticle of the thick- 

 ness found covering hard seeds should exist without a frame- 

 work of some kind, but nmch more likely that it should be 

 formed by the deposition of cutin within the substance of the 

 original cell wall (or some modification of it), which, in conse- 

 quence, would increase greatly in thickness. The particles of 

 cutin would be evenly distributed among the micellae of the 

 cellulose forming the framework. 



If such seeds were treated with fat solvents the waxy materials 

 should be dissolved out, and the insoluble basis be left, and it 

 would be possible to detect the presence and nature of the 

 latter by using suitable stains. If an outer membrane can be 



