142 



all 



are partition walls occurring with no dependence upon division 

 of nucleus, also the threads or beams (balken), as they are called 

 in German, which are thrown across from wall to wall, apparently 

 as supports. These appear first as protoplasm strings, and are 

 afterward transformed into cellulose. Catilerpa is not the exam- 

 ple referred to. 



Other plants submitted to this test were Codhim tomentosmn 

 and C. Bursa, Dasycladiis clavceformis, Udothea cyathiformis. 

 Polysiphonia variegata and a few out of the Cladophoraceae, 

 of which gave similar results as to the question of apposition. 



The author concludes from these results that, in general, the 

 growth of cell membrane depends on apposition, and that there 

 remains no longer any direct proof of growth by intussusception. 

 Not having access to the original article, it is impossible to 

 determine from the review just what the author means in refer- 

 ence to the manner of growth in surface of a cell wall after the 

 foundations are once laid. This is one great difficulty in the 

 apposition theory, which offers no satisfactory explanation of the 

 phenomenon called surface growth, that is, growth in the other 

 two dimensions before growth in thickness begins. The only 

 reference to this point is the one quoted, in which the author 

 refers such growth to the stretching of the wall caused by the 

 influence of the protoplasm. Also at the end of the review it is 

 stated that the author believes with Sachs and de Vries that all 

 growth is dependent upon turgor, and holds Krabbe's view essen- 

 tially wrong; further, that the acceptation of turgor as the neces- 

 sary condition to growth excludes the necessity of the notion ot 

 growth by intussusception. 



How this excludes such necessity is not made clear in the 

 review. Neither does it appear by this experiment that growth 

 by intussusception is, with absolute certainty, disproved in the 

 case of surface growth. For allowing that it does take place, 

 that new uncolored particles of cellulose are shoved in between 

 the old colored particles, the only visible effect of this would be 

 to render the color of the old membrane lighter blue and it seems 

 this is exactly what does take place of itself, as he states, In living 

 plants — the color fades in a few hours. 



There is also one other point of interest not referred to, that 



