158 PKACTICAL BOTANY. 



ii. The Nucellus, a mass of parenchyma, near the 

 centre of which is 



iii. The Embryo-sac or Macrospore, a cell much 

 larger than those of the surrounding tissue and lying 

 some distance below the apex of the nucellus. 



Pollen-grains may often be found seated on the apex 

 of the nucellus, one or more of these may throw out 

 Pollen-tubes, which penetrate into its tissue. 



Dissect off one whole Ovuliferous scale, and observe 

 on its upper surface, close to the base, two Ovules, 

 which are anatropous. Note also the relative positions 

 of the two sets of scales. 



B. Take cones of the stage above described as (b). 



The materials should be collected about the middle of June, 

 and must be hardened in alcohol. 



Strip off the ovulifero^is scales of such cones. The 

 ovules will remain adherent to the base of each. Cut 

 longitudinal sections of the scales so as to pass through 

 the median planes of the ovules ; mount in pure glyce- 

 rine, and examine with a low power. Observe 



1. The structure of the Ovuliferous scale, which is 

 traversed by vascular bundles, and resin-passages. 



2. The Ovule, which is united with the scale, and 

 consists, as in the younger stage, of 



a. An external Integument. Note the wide 

 micropyle ; 



I. The Nucellus; 



c. The Embryo-sac filled with Endosperm. All 

 the parts of the ovule are larger than in the younger 

 stage, but retain the same relative positions. Note 

 carefully that Pollen-grains (one or more) are usually 



