

SEED 127 



Remove the seed-coat, which is brittle and easily cracked ; 

 note beneath this a thin papery white layer, the tegmen of old 

 writers : this closely invests the white oily mass of the endo- 

 sperm, a tissue which is not present at the period of 

 maturity in any of the seeds above described. Cut this through 

 transversely : and a flattened central cavity will be found, lined 

 on either side by one of the thin flattened cotyledons of the 

 embryo. Lay open the endosperm of another seed longi- 

 tudinally, by a cut following the plane of the flattened cavity : 

 it will then be clearly seen that the straight embryo is embedded 

 in a mass of endosperm, and that it consists of two cotyledons, 

 radicle, and plumule. 



Longitudinal sections should be cut of the mature seed of 

 Caltha for microscopic observation under a low power, and the 

 relative positions of the firm testa, the endosperm, and embryo, 

 are to be observed, together with details of their structure. 



(B) Monocotyledons. 



II. Soak fruits of the Maize (Zea Mais} in water for several 

 hours. The fruit is a caryopsis, and results from the develop- 

 ment of both ovule and ovary ; its form is compressed conical, the 

 apex of the cone being the basal point of attachment of the fruit. 



Strip off the external coat of the fruit : this represents 

 both the wall of the ovary and the integument of the ovule. 

 Distinguish in the body of the fruit which remains 



1. A lateral, smaller, white portion : this is the embryo. 



2. A larger yellow part, which forms the greater mass of the 

 fruit : this is the endosperm. 



Separate the embryo from the rest, and note its shape. 



III. Cut longitudinal sections of the fruit so as to traverse 

 the embryo in a median plane : mount in glycerine, and 

 examine with a low power : observe 



i. The coat of the fruit, consisting of two layers, the pericarp, 

 and seed-coat. Note at the apex of the fruit the remnant of 

 the style, and the scar of attachment at the base. 



ii. The endosperm, consisting of thin-walled parenchyma ; 

 the cells contain polygonal starch-grains, embedded in a matrix 



