IN RELATION TO EVAPORATION. 



119 



The same protection from change is witnessed, as is well known, in vegetables, 

 from the removal of their aqueous portion. And in them, too, the cuticle 

 appears to act a part in many instances similar to that of the animal cuticle in 

 retarding evaporation. I may mention an instance or two in illustration, select- 

 ing a tuber, the potato, and a fruit, the apple, these being striking examples : — 



On the 22d June, three potatoes of the kidney kind were taken from the 

 ground : one (No. 1) had its skin left on — it weighed 295*2 grs. ; another (No. 2) 

 had its outer skin removed — it weighed 181*7 grs. ; a third (No. 3) had its outer 

 and very fine inner skin both entirely removed — it weighed 263*2 grs. They 

 were placed on the chimney-piece, where the temperature throughout the year 

 varied inconsiderably, ranging from about 50° to 60°. The three were weighed 

 from time to time ; the loss per cent., as found on each weighing, is given in the 

 following table : — 



June 



24. No 



1 lost 



7 8 per 



cent 



, No. 2, 46-5, 



No. 



3, 54-0 



u 



27. 



)> 



88 



39 



„ 66*4, 



ii 



70'2 



33 



30. 



>) 



104 



33 



„ 72-6, 



ii 



73-3 



July 



6. 



)? 



11-4 



33 



„ 74-9, 



33 



75-8 



n 



11. 



11 



12-6 



33 



„ 75-7, 



33 



77*8 



>> 



22. 



)> 



13-1 



3) 



„ 75*8, 



33 



78-6 



August 



5. 



j) 



13-9 



>> 



„ 75-9 ; 



33 



79-8* 



September 



10. 



93 



15-8 



)> 



No further loss 



33 



85*7f 



December 



1. 



53 



21 -0| 



I) 





33 



862 



February 



2. 



>» 



27*5§ 



3) 



No further loss 



March 



14. 



3> 



32-7II 



3> 









In these instances it is seen, that not only is the loss of water, owing to 

 evaporation, retarded by the cuticular covering, but also that the vitality or ger- 

 minating power of the tuber is destroyed by its removal ; and further, that the 

 removal of the outer delicate cuticle has much the same effect in promoting 



To what extent these portions of meat and fish might otherwise be altered, and their nutritive 

 quality impaired, is a question I am not prepared to answer. I may mention that white of egg, 

 which, on thorough desiccation at a low temperature, is again for most part soluble, appears, if long 

 kept, to become insoluble, judging from a trial of some put by after desiccation in 1852, and recently 

 examined. 



* Now, August 5, No. 1, where least exposed to light, has become greenish ; where most 

 exposed, brownish green. 



No. 2 has become dark brown, almost black, and has acquired a crescentic form, contracted, 

 without being shrivelled. 



No. 3 has become of a light brown, and is much shrunk and shrivelled. 



f Now, September 10, on No. 1, three small greenish sprouts have appeared tipped with black ; 

 general hue the same. Nos. 2 and 3 of the same colour and appearance as before. 



I Now, December 1 , the sprouting buds of No. 1 have grown a very little, showing a very 

 feeble vitality, and very slow progress. In Nos. 2 and 3 no apparent change. 



§ Now, February 2, the bud of No. 1 has grown into a stalk, with terminal greenish leaflets, 

 and three lateral long roots, with delicate spongioles. 



|| Now, March 14, the tuber No. 1 is slightly shrunk; the stem from it is *9 inch in length, 

 and -3 inch in diameter where thickest; is of a dark purple, and is surmounted by several small 

 green leaflets ; the roots from its side, numbering five, vary in length ; the longest is 1*7 inch. 

 Weighed again on the 28th of May, the tuber was only a little more shrunk; it was reduced to 

 161-5 grs. The growth from it, the stem, leaflets, and other offshoots, had all a healthy appearance. 



VOL. XXIV. PART I. 2K 



