148 PRACTICAL BOTANY 



material should be collected about the middle of June, and 

 must be hardened in alcohol. 



Strip off the ovuliferous 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 glycerine, 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. 



b. The nucellus as before, but larger. 



c. The embryo-sac, filled with the thin-walled tissue of the 

 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 to be 

 found lying on the apex of the nucellus, and that from the 

 larger cell of each of them arises a cylindrical pollen-tube, which 

 traverses the tissue of the nucellus as far as the apex of the 

 endosperm, where it widens out into a large sac. 



Observe near the apex of the endosperm, and embedded in 

 it, one or more large vacuolated protoplasmic bodies : these 

 are the egg-cells, or ova. From the apex of each a small cell 

 is cut off shortly before maturity : this is the ventral canal cell. 

 Leading upwards from this (i.e. towards the micropyle) may be 

 traced a narrow neck or channel, inclosed by smaller cells than 

 those of the surrounding endosperm. The neck, ventral canal 

 cell, and ovum, together form the archegonium. 



III. Remove ovules from cones of the second year, taken 

 and preserved in alcohol about August I. Dissect off from 

 them the now hardened integument or seed- coat : note within 

 this the delicate remnant of the nucellus, which covers the 

 mass of endosperm. Soak the latter in water, and dissect 

 from it with needles the numerous embryos, which lie in the 

 central cavity of the endosperm : treat them with potash, and 

 mount in dilute glycerine. Examine with a low power, and 

 observe 



