V 























rN VEGETABLE BIOLOGY, 



507 

























perfectly open, jusfc as at the beginning of the vegetative period, 

 and they gave the purple colour with Schulze's solution. It has 

 not been thought necessary to draw the stages of this process ; 

 but anyone who wishes to see figures of what occurs will be able 

 to satisfy his curiosity by referring to tab. 9 of Janczewski's 

 memoir*, where dissolution of the callus of ArktolocHa Sipho 

 at the beginning of the season is beautifully figured. Fig. 10 on 

 .Plate XIV. shows the sieves cleared of their callus : in this case 

 the action was allowed to continue for 30 hours, by which time 

 neither the callus in the acid solution, nor that in the water, had 

 been in any way affected. 



In this second point, therefore, we see that the callus of the 

 vegetable-Marrow agrees with the great body of proteids. We 

 have already found Eussow drawing a parallel between callus and 

 proteids, on account of the behaviour of the former to iodine and 

 to aniline-blue ; and there can be no doubt but that Eussow was 

 upon the right clue, and that the starchy-mucilage view must, at 

 least so far as relates to the Vegetable-Marrow, be definitively 

 abandoned f. 



It is to be presumed that peptone is formed as the result of the 

 digestion of callus ; but this I was unable to ascertain, apparently 

 because of the extremely small amount of callus dealt with. It 

 would seem that to get the peptone reaction with clearness, a 

 much larger quantity of callus than I had must be employed. 





























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Or 



•Mabeow 



















The chief objections which have been urged against the swelling- 

 up theory of callus-formation are, that the edge of the sieve is 

 always visible, although plenty of callus may be present ; that in 

 the progress of obliteration the connecting channels, at first rela- 

 tively broad, become thinner and thinner, the sieve-plate mean- 

 while not itself i 



Bu 



increasing in size + 



and in connection with this, 



» 



§ 







. 





















Mem. Soc. Sc. Nat. Math. Cherbourg, xxxii. (1881). 



t Gardiner also at first supported Bussow (Phil. Trans. 1883, and Proc. 



Ca mb. Phil. Soc. 1884, p. 101); but he afterwards changed sides (Proc. Can.b. 



p hil. Soo. 1885, p. 230). Hillhouse (Midland Naturalist, 1884, p. 122, note) 



notices some resemblance, " probably, however, merely casual," between the 



factions of callus and those of nuclein. 

 tFisch 



er, 1886 Memoir. 



30-32 





§ Sitzb. Dorpat. Naturf. Gesellsch. 1882. 



.... . 





2w 2 





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