ANIMAL AND VEGETABLE 133 



lecture Sachs said : " It appears that the fats can pass 

 through the closed tissue-cells as such ; though of course 

 the greater part of them is transformed into starch and 

 sugar for transport and use. Similar phenomena with 

 respect to fats occur moreover in the animal body, where 

 the fats entering into the stomach are in the first place 

 emulsified by the secretion from the pancreas, that is, 

 they become converted into exceedingly fine drops and 

 then saponified. . . . The presence of fats in the seedling 

 can only be explained by assuming that glycerine and 

 fatty acids travel from cell to cell, and are continually 

 becoming reunited for the formation of fat." 



In the case of plants in dry climates, or so situated that, 

 for any reason, transpiration from their outer surfaces 

 must be diminished, they are characterised by the greatly 

 thickened and cuticularised walls of their epidermal cells. 

 Deposits of wax are also present in the cutinised layers of 

 the epidermis, and consequently water will flow off from 

 the epidermis without wetting it. The wax is sometimes 

 spread over the surface of the cuticle as a wax covering. 

 This is the case in most fruits, where, as is so noticeable in 

 plums, it forms the so-called bloom. (Strasburger.) 



There can, I think, be no doubt that the main purpose 

 underlying the provision of the wax covering of fruits is 

 the preservation of their absolute insulation, and one can 

 be sure, even without examination, that where the outer 

 skin or rind of a fruit is of comparatively delicate texture 

 as of the plum while the fruit itself is juicy and highly 

 conductive, the protective " bloom " will be found to be 

 most abundantly provided. 



There is at least some analogy between this and the 

 sebaceous secretion of the human epidermis ; both are 

 apparently designed for the performance of the same 

 function. 



In cases where wax is absent or in greatly diminished 



