128 THE OAK. 



above diagram will serve to represent the lateral buds 

 which develop male inflorescences only, or if we suppose 

 the three bracts F, a, and /3 away, it would serve for a 

 terminal bud. 



Each single female flower stands in the axil of a 

 minute scale on the floral axis, as said, and its general 

 structure has been described. When the pollen grains 

 have been dusted on to the trifid stigma, about the end 

 of May or beginning of June, each grain germinates and 

 sends a minute tube down the style, and this pollen-tube 

 soon reaches the cavity of the ovary, and its end becomes 

 applied to one of the ovules. While the pollen-tube is 

 descending the style, the ovules have arisen as minute 

 cellular outgrowths from the angles of the three cham- 

 bers of the ovary (Fig. 34, d). There are two in each 

 chamber. Each ovule is at first a mere solid lump of 

 cells (nucellus), which curves and becomes enveloped in 

 two thin investing layers, called integuments, as shown 

 in the figures A-D (in Fig. 35). Inside the solid nucellus, 

 n, of the ovule there soon arises a small cavity filled with 

 nucleated protoplasm, and termed the embryo-sac, e, be- 

 cause the embryo is to be developed in it. 



This embryo-sac contains, among other structures, a 

 minute, nucleated, naked mass of protoplasm, called the 

 oosphore, or egg-cell. The pollen-tube has carried down 

 in its apex also a nucleated mass of protoplasm, and it 

 passes this over into the egg-cell in the embryo-sac ; the 

 union of the nucleus from the pollen-tube with the 

 nucleus of the egg-cell constitutes the act of fertiliza- 



