IQ2l] 



PA CK—J UN I PER US 



35 



Fig. i shows the structure of the seed of /. virginiana, with its 

 many membranes and protective layers. In strong contrast with 

 the hard brown coat are the clear white endosperm and embryo. 

 The hard coat consists of three layers: the outer fleshy (a), the 

 stony (b), and the heavy inner fleshy (c). In the outer fleshy 

 layer are found pectic substances and methyl pentosans. The 

 stony layer is lignified and contains other substances, as calcium, 

 pectates, and pentoses. The inner fleshy layer is well developed 

 and consists of suberin with some little cellulose. Of the endosperm, 

 embryo, etc., one distinguishes the nucellus (d), the mass of dis- 

 torted tissue (e) , the hypocotyl cap (/) , the megaspore membrane (j) , 

 the endosperm wall (k), the endosperm (g), and the embryo (h). 



TABLE II 



Percentage of imperfect seeds in lots i, 3, 4, and 5 



Species 



J. virginiana 



J. virginiana 



J. virginiana 



J. virginiana 



J. communis. ...... 



J. prostrata 



J. virginiana *. . 



The nucellus is constructed of long narrow cells which give tests for 

 cellulose and pectic acid. The mass of tissue (e) protecting the 

 hypocotyl consists of cellulose, pectic substances, and some other 

 groups of substances such as fats and gums. Between this mass 

 and the hypocotyl is a cap of very fine and firm cells (i), which are 

 made up of cellulose and hemicellulose. The megaspore mem- 

 brane (;*) is very thin and stains with ruthenium red. Examination 

 shows that the outer wall of the outer layer of endosperm cells 

 has been developed into a suberin wall (k) . This wall is insoluble in 

 concentrated H 2 S0 4 , 50 per cent chromic acid, and gives the phellic 

 acid reaction. The endosperm cell walls are rather thick and 

 made up of cellulose. Cell walls of the embryo arc thin and con- 

 sist of pectose and cellulose. 



