160 



MISSOURI BOTANICAL GARDEN 



of the central row 



growth of 



cortical cells to several layers in thickness has not been 

 sufficiently studied to make clear the method of growth. 



tates that the 



In 



treating 



of D 



Jon 



s 



divisions of the cortical cells are radial and that the outer 

 cells only divide. As the structure of Mesogloia is quite 

 similar to that of Desmarestia as described by Jonsson, it 

 seems plausible that the same division may occur here. 



The above investigation was suggested by Dr. Bradley 

 M. Davis of the University of Chicago, to whom I am 

 indebted for several valuable suggestions. 



EXPLANATION OF PLATE. 



* 



Plate 38. — 1, Median longitudinal section of the apex of the stem of 



Mes 





<7, paraphysis, X G0 °* 2 > Longitudinal section of stem near apex, 

 through primordia of a branch: lettering the same as in figure 1, X <>00. 



3, Cross section of stem just back of apex, showing cortical cells, X G0 °- 



4, Cross section of stem further from apex, showing thickening of the 

 walls of the cortical cells to form the central cylinder, X 60 °- o> Hair 

 nearly mature, X co °- C, Cell from the central row, near the apex, X 



720. 



7, Origin of branch from cell adjoining central row of cells 

 >tage than that shown in fkrure 2. V 3f>0. 



a 



* Kentniss des Baues und der Entwicklung des Thallus bel den Des- 

 marestiaeen. (Lunds Universitets Aarskrift. 37. Afd. 2. No. 6.) 



