370 



sm J. litbbock: — phytobiological observations. 



many cases tlie cotyledons are what is called "incumbent," that 

 is to say the radicle is folded npon one of the cotyledons, and .in 

 such species the outer cotyledon is often rather larger than the 

 other, as for instance in llesperis matronalis. 



Yig. 74. 



Fig. 





Pig. 78, 



Fig. 76. 



Fi^:. 77. 



Ixaphamta sativits. 



75. 



Embryo 



Fig. 74. Outline of seed, x 4: m, micropyle ; A, biluni. Fig. 



extracted from seed, X 4. Fig/76, Embryo, X 4; vertical section. 

 Fig. 77. Embryo, seen from the side, x 4: o.c^ outer cotyledon; 

 i.c, iuner cotyledon; r,_ radicle; t, testa. Fig. 78. Germinating 

 seedling, X 2, showing the cotyledons still folded. 



In the Mustard (fig. 3), Cabbage, Eadish {Eap'hanus),va\^ some 

 other Crucifers the diflerence is more marked, and is due to a 

 different cause. The cotyledons, as just mentioned, are applied to 

 one another face to face (figs. 75-77), and then doubled longitu- 

 dinally one inside the other. The outer one, therefore. Laving 

 more space, becomes larger and the petiole is longer. In Cerent 

 (fig. 79) the embryo is much curved, and the cotyledons bemg 

 thick and fleshy, the inner one is naturally smaller than the outer. 



In Ahronia nmhellata (^g. 80 B) the embryo is large, much 

 curved or doubled on itself, and lies outside the perisperm, the 

 two edges of the cotyledon reaching almost to the radicle. The 

 second cotyledon (ic) is minute, generally not more than one 

 seventh the length of the outer one, though in one seed it attained 

 nearly half the length of the other. In another species of the 



