134 PRACTICAL BOTANY. 



derived from the hypophysis, the hypocotyledonary stem 

 from the lower tier of octants. 



5. Other parts as before. The Apical cone or 

 Plumule formed between the cotyledons. 



ii. Monocotyledon. 



Treat ovules of Alisma Plantago in the same way, 

 and observe the following stages of development : 



1. Suspensor and Embryo consist of a single short 

 series of cells, produced by transverse divisions. 



2. The terminal cell divides longitudinally into four 

 (first tier). 



3. The second, third, and fourth cells from the end 

 also divide successively (second, third, and fourth tier). 



4. The cells of the body of the embryo divided (as 

 in Capsella) so as to form three layers (a) external 

 Dermatogen, (&) Periblem, (c) central Plerome. 



5. A lateral depression of the surface, at the level of 

 the second tier. At the basal lip of this the Apical 

 cone of the plumule is formed. 



The single Cotyledon is formed from the first tier. 



The Radicle from the third tier. 



The Apex of the root from the fourth tier. 



Compare these results with those obtained in 

 Capsella. 



For obtaining preparations of the embryo in situ, and 

 of the Endosperm surrounding it, the ovary of species 

 of Potamogeton will be found to be good material : it 

 should be previously hardened in spirit. 



Cut longitudinal sections of a single carpel, parallel 

 to the flattened sides : they should not be cut too thin. 

 Mount in glycerine, and examine with a low power. 



