122 FAMILIAR LESSORS lis BOTAJSY. 



expansion of the apex of the funiculus; this is called an 

 (35) aril. Some seeds are formed entirely by the embryo, 

 as in the bean; others again have the embryo packed 

 away with a mass of albumen, as in the four-o'clock. The 

 former seed are said to be (36) exalhuminous, the latter 

 (37) alhicminous. 



You were merely told of the three rudimentary parts of 

 the plant as forming the embryo : cotyledons, plumule, and 

 radicle. The radicle of the embryo always points toward 

 and is near to the micropyle of the seed : if the embryo is 

 straight, or merely partakes of the curvature of the seeds, 

 the cotyledons point to the opposite extremity ; that is, to 

 the chalaza. 



The position of the radicle varies in respect to the 

 liilum. In orthotropous seeds the radicle points away 

 from the hilum: in the anatropous form, the extremity 

 of the radicle is brought to the immediate vicinity of the 

 hilum ; and this is the case, though in a different way, in 

 the campylotropous seed. 



The embryo and the albumen do not always occupy the 

 same relative parts of all seeds. For instance, in wheat, as 

 in all cereal grains, and grasses, the embryo is placed 

 laterally at the base of the albumen; then again, it sur- 

 rounds it ; in other cases, is surrounded by it. When the 

 embryo is external, and curved circularly round the albu- 

 men, it is said to be (38) perii^lieric ; when bent in such a 

 way that the radicle lies along the edges of the cotyledons, 

 the latter are said to be (39) acumhent ; when the radicle 

 rests against the back of one of them, or near to it, they are 

 (40) incumhent. 



The direction of the embryo with respect to the pericarp 

 is also of importance to the student of natural classifica- 

 tion. The terms (41) ascending, or radicle superior, are 

 employed when the latter points to the apex of the fruit ; 

 descending, or radicle inferior, when pointing to the base ; 

 (42) centripetal, when the radicle is turned toward the 



