Studies on the Binucleate Phase in the Plant-cell. 15 



no essential respect from those of the other examples described in 

 the present paper. 



|g In the young flowering axis oi Hemerocallis fidva binucleate and 

 trinucleate cells are common in the ground tissue, and I have 

 observed prophase and spindle stages and phragmospheres. The 

 chief interest of this plant however is that it furnishes particularly 

 •definite evidence as to the fate of the nuclei ; * the cells apparently 

 become uninucleate by the degradation and disappearance of one 

 member of the pair. Pairs of nuclei from individual cells, one of 

 which seems to be degenerating while the other remains more or 

 less normal, are shown in PL I, figs. 33, 36, and 37. 



I have also examined the leaves of Hemerocallis fulva, and have 

 observed binucleate cells and phragmospheres in the mesophyll of 

 the basal region of a young leaf. This is the growing region, as I 

 have demonstrated by marking off the leaf with Indian ink into 

 zones of 1 cm. and measuring the growth of the zones. The 

 -epidermal cells show a peculiarity which may be mentioned here. 

 They are always, so far as I have been able to observe, uninucleate, 

 and in the younger stages the nuclei are rounded, but later on 

 they become very markedly bilobed (PL I, figs. 34 and 35). This 

 lobing is obviously not a case of degeneration or senility, as it occurs 

 in very young leaves ; I have found it for instance in leaves gathered 

 on January 28, 1916. The nuclei are sometimes so deeply bilobed 

 as to be almost bisected, but we have no evidence that actual division 

 into two ever takes place. The lobing is probably comparable 

 with that observed in the young roots of Stratiotes.'\ 



Nothoscordum fragrans shows very numerous binucleate cells 

 in the ground tissue of the young inflorescence axis. One or two 

 phragmospheres with paired nuclei wei:e observed, but the material, 

 which was gathered on April 29, was probably rather too old to 

 show many cells in process of becoming binucleate. The resting 

 nuclei are of a curious irregular form, the significance of which I 

 propose to consider in a later paper. 



I have examined a young leaf of Alisma Plantago gathered 

 on May 5, 1916. It showed some typical phragmospheres with 

 paired nuclei (PL I, fig. 38), and various earlier karyokinetic stages. 

 A young inflorescence axis, also, was collected on June 10. Many 

 cells of the ground tissue were binucleate, but the material was 

 apparently too old to show phragmospheres. 



8. Polygonum cusjpidatum Sieb. et Zucc. (PL I, figs. 25 

 and 26). 



The stem of Polygonum cuspidatiim Sieb. et Zucc. was ex- 

 amined because this appears to be the plant in which, under the 



* Beer, R. and Arber, A. (1919), p. 12. f Arber, A. (1914), and see pp. 19-21. 



