384 



Reed and Smoot : Polygonum virginianum 



longitudinal section (fig. 3) shows that the reinforcing sclerenchyma- 

 tissue is intersected by the separation-layer, thus materially weaken- 

 ing the mechanical tissue at that point. 



Many longitudinal sections show a splitting of the marginal 

 portion of the separation-layer as the fruits approach maturity. 

 This was interpreted to mean that the cells of the cortex had lost 

 part of their water content, and consequently had shrunken. When 

 the cortical layer is thus cleft, the subsequent ejection of the 



Fig. 6. Longitudinal section of pith at the separation-layer. A, separation-layer; 

 5, pith-cells on distal side of separation-layer ; T y pith-cells on proximal side of sepa- 

 ration-layer. 



achene is entirely dependent on the pith and mechanical tissue. 

 The careful examination of several hundred sections failed to give 

 any evidence which would confirm Kerner's statement that the 

 cells of the cortical parenchyma become Iignified. On the contrary, 

 we found that the cortex plays no part whatever in producing the 

 tension which ejects the fruit. 



In order to learn whether any of the tissues of the pedicel 

 were hygroscopic, they were subjected to moisture, with subse- 



