MARGARET B. CHURCH 



339 



outer or cork cells arc crushed and killed, and the vascular colls 

 arc thickened. The outer cells are crushed doubtless, but do 

 they die first, are they killed by the crushing? His further con- 

 clusion that the vascular cells thicken may be true, but where is 

 his proof? To return to the active or endodermal cells — how 

 can we accept the statement that because a cell lengthens in one 

 direction therefore it must necessarily shorten in another? Vol- 

 ume being constant and cell wall composition and tension being 

 similar at every point this would be true. But Rirnbach did not 

 investigate these points. 



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1 



Fig. 1. Section of root of Cooperia Drummondii. The scale is equal to 0.1 mm. 



Rirnbach states that ripples may be seen on the root surface 

 even to the root-ends with the naked eye. Microscopic slides 

 have proven to the writer that the process of root contraction 

 is well under way in a five-day-old seedling of Cooperia Drum- 

 mondii at points not visible to the naked eye. The ripples in in- 

 dividual cells in the case of C. Drummondii are not confined to 

 radially placed cell walls as Rirnbach finds them to be in the 

 species which he investigated. On the contrary they may be 

 found on walls running in any direction. In some stages they 

 are so fine as to be distinguishable only with the oil immersion 

 objective, but always numerous cells with rippled walls may 

 with care be detected in the parenchyma cells of the root with 

 a combination of 10 ocular and 8 objective. 



