ZOOLOaT AND BOTANY, MIOKOSCOPY, ETO. 765 



Pisum sativum, Phaseolus multiflorus, and Physostigma venenosum ; 

 (3) those containing coarsely granular aleurone and a fatty oil, as 

 Jjupinus mutahilis and Trigonella Foenum grcecum. Those of Abrus 

 prcBcatorius constitute a distinct type ; they contain a fatty oil and 

 albuminoids in the form of finely granular protoplasm, but neither 

 aleurone nor starch. Another characteristic is the persistence of the 

 nucleus and nucleoli in the peripheral parenchymatous layers of the 

 cotyledons. The crystals sometimes found in the parenchymatous 

 cells destitute of nucleus may consist of stearic acid or hesperidin. 

 The cell-wall is thickened in a porous manner, is not doubly refrac- 

 tive, and consists of pure cellulose. The testa is composed of four 

 layers, viz. : — (1) rods, colourless in the red part of the seed, while 

 in the black spot they are of a purple-violet colour; (2) palisade- 

 cells, distinguished by their length, their branching, and by the 

 folding and small diameter of their lower end ; (3) parenchyma, com- 

 posed of cells elongated in the tangential direction ; (4) albumen, the 

 cellular nature of which is clearly defined in the first layers, while 

 the cells at a greater distance lose their individuality by becoming 

 flattened radially, and at length coalesce into a homogeneous pellicle, 

 which cannot be decomposed into its separate cells even by macera- 

 tion in chromic acid. In caustic potash this pellicle swells up 

 strongly, and forms local projections. The hilum has two of the 

 layers of rods, but no palisade-cells, these being replaced by scleren- 

 chyma. With the exception of the albuminous layers the cell-walls 

 display distinct cellulose-reaction. By chloride of iron the presence 

 of tannins can be recognized in the albuminous layers and rods. 



Comparative Anatomy of Cotyledons and Endosperm.* — J. God- 

 frin states, as a general result of a comparison of the structure of the 

 embryo and the endosperm, that those embryos the cotyledons of 

 which contain starch, whether alone or together with aleurone, are 

 never accompanied by endosperm. Those, however, which contain no 

 aleurone, even when thick (as Amygdalus, Armeniaca, Prunus, Corylus, 

 Juglans, Carya, &c.), may contain an endosperm, which is however 

 always very small. Embryos with thin or foliaceous cotyledons, are 

 not necessarily accompanied by endosperm, as witness Hedysarum 

 sihiricum, Casuarina quadrivalvis, Grevillea robusia, Eakea saligna, and 

 Acer. 



The author classifies cotyledons under two heads : thick or tuber- 

 cular, and thin or foliaceous. The former, when mature, have a 

 simple epidermis without stomata or hairs, and in the interior a thick 

 parenchyma with large globular cells, between which are a number of 

 air-cavities. On germination very little modification of the tissues 

 takes place. Foliaceous cotyledons have, when mature, a simple 

 epidermis, often provided with stomata more or less developed ; the 

 parenchyma is much smaller in mass, but is always divided into two 

 distinct layers. They vary greatly in their mode of development 

 during germination. In those which contain aleurone its absorption 

 is the first indication of germination. 



♦ Bull. Hoc. Bot. France, xxxi. (1884) pp. 44-51. 



