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IK VEGETABLE BTOLOGT. 517 



among true proteids, or relegated to the miscellaneous group of 

 bodies allied to proteids ? Bearing in mind that all three 

 proteid reactions are given, I think it would be better to include 

 it among true proteids, where, on account of its resistance to 

 gastric digestion, it will take its place alongside of lardacein. 

 ft the bodies allied to proteids with which the substance might 

 possibly be compared, Mucin gives only two of the proteid 



reactions 



eadily 



in alkalis. Chondrin is soluble in hot water, in alkalies, and 

 ammonia. Gelatine swells up in cold and dissolves in hot water 

 and in weak acids and alkalies, and it has, moreover, extremely 

 feeble proteid reactions. Elastin, with feeble proteid reactions, is 

 soluble in Hydric Sulphate and Hydric Nitrate, whereas Nuclein 

 gives but an iudistinct xanthoproteic reaction, and none at all 

 with Millon's fluid. These differences are all of them of such 

 importance, that there can hardly be a doubt of the desirability of 



not classifying the substance of Ballia stoppers with these 

 bodies. 



Some General Considerations. 

 Sachs's * theory that it is in the sieve-tubes that proteids are 

 constructed, has not found much favour. The general view now 

 18 tnat adult sieve-tubes are merely distributors of proteids, not 

 manufacturers of them, for they soon become enucleate t. The 

 notion hinted at by Sachs $. seems to be a good one ; the callus 

 according to this is interposed as a mechanical hindrance to the 

 passage of the contents of the tubes j in support of this may be 

 cited Briosi's § observation that starch-grains sometimes actually 

 stick in the sieve-plates, as a proof that some mechanical hin- 

 drance is necessary. I cannot help thinking that Ballia 

 stoppers must function in the same way. What is certain is 

 that the size of the pit increases with the growth of the septum, 

 so the older a cell is, the wider will be the pit separating it from 

 adjacent cells. The lower cells of the main and secondary 

 branches ultimately become of great relative size, 



and 



(Engl, transl. 



P. 325). 

 H. von 



>• That sieve-tubes are organs for transport of proteid was held by 

 Mohl, Bot. Zeitung, 1855 ; Nageli, Siteb. bayer. Acad. Wiss. 1851 , 









Hanstein, Mitchsaftgefjisse ; Sachs, Flora, 1863, &c. 

 t Fischer, Unters. iib. d. Siebrohrensyst. d. Cucurbitaceen 



ft ' 



4 Vorlesungen, no. xxii. (Engl, transl. p. 361). 

 § Bot. Zeitung, 1873. 







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