1914] SNOW— DIAPHRAGMS OF WATER PLANTS 503 



B. OF DIAPHRAGMS 



Leitgeb (18) states that he cannot account for the fact that 

 some cells do not pull out, but remain as diaphragms. Meyen 

 (21), studying Scirpus lacustris, and Falkenberg (12), studying 

 Typha leaves, state that diaphragms result from stellate paren- 

 chyma by a separation of this tissue intc 

 (5) finds that the diaphragms in the leav< 

 arise from small cells cut off from the o 



CUNNINGTON 



• • 



m 



small cells increase in one ulane and form 



m 



them 



Scirp 



diaphragms. In Juncus effusus the parenchym 



which 



Scirpus a similar layering may 



In longi- 



The cells of some of the layers retain their meristematic character 

 and continue to divide and to keep pace with the growth of the 

 surrounding tissues, thus forming diaphragms. The other cells 

 become stellate by the process already described (figs. 2,x, 12. 13). 



C. OF THE GROUPS OF CELLS IN THE DIAPHRAGMS 



Several writers have noted or figured the diaphragm cells in 

 groups of four. Duval-Jouve (9) reports this arrangement 

 for several species of plants, but offers no explanation as to the 

 origin of the groups. DeBary (6) believes each group of cells 

 in the diaphragms of Scirpus lacustris to originate from one 

 mother cell. 



From a comparison of figs. 12 and 13, it seems evident that such 

 an origin as that suggested by DeBary is reasonably probable. The 

 number, however, is not invariably four, but groups of three and five 

 also appear (fig, 6). The reason for the formation of two, three, 

 or four walls parallel to the long axis of the cell is not easily explained 

 in terms of cytological mechanics. It was suggested to me that a 

 study of the adventitious buds of flax seedlings might throw light 

 upon the subject. Flax seedlings were grown, therefore, until the 

 cotyledons had opened, and were then decapitated. After about 



