

h 



1917] DENNY— PERMEABILITY 477 



Membrane of squash {Cucurbita maxima) 



This is the greenish membrane surrounding the cotyledons, and 

 is obtained from soaked seeds by first removing the horny white 

 spermoderm layer, and then removing the greenish coat from the 

 cotyledons. At d (fig. 3) is the greenish layer; at is a compressed 



>osed of cellulose and pectin. The inner 



com 



erm 



pletely filled with fatty substances. The walls are thin and are 

 of cellulose and pectin. In 



some 



tions were positive in layer 

 d,but most tests were neg- 

 ative. No tannins were 



d 



I 



mem 



branes were absent. 



m 



Fig. 3. — Cross-section of seed coat of Cucurbita 

 maxima, X450. 



It is believed that the high resistence to the flow of water 

 through this membrane is due to the high content of lipoid sub- 

 stances in layer /, m. These substances are almost entirely 

 removed by treatment with lipoid solvents, and a large increase 

 in permeability results. It is worthy of note that although this 

 membrane is highly resistant to the passage of water through it as 

 compared with other membranes, distinctly suberized layers do 

 not enter into its composition. 



Membrane of almond (Prunus Amygdalus) 



Large cells/ (fig. 4) were found to extend from the outer surface 

 of the seed coat. These were in some places much distorted in 

 shape and they also did not cover the entire surface. The walls 

 were of cellulose and pectin, and protein tests gave positive results 



.1.1 ... . . . . e 1 > __11 11„ 



in this layer. 



parenchymatous 



giving cellulose and pectin reactions. A suberized layer is found 

 at e and tannin reactions were positive in this region. At m again 

 is a layer of compressed parenchymatous cell walls. The endo- 

 sperm layer is at 0, s. The cells are filled with fatty substances (0), 

 and the cell walls s are composed of cellulose and pectin. These 

 walls are not thick as compared with either the Citrus or Xanthium 

 coats. The cell contents also are not completely removed by 

 extraction with lipoid solvents. 



