Blosso?n and Seed 207 



needs warmth, the germ or embryo does not begin to 



form in the ovules until the following May. 



The ovules of the American oak wait almost a year 

 after the entrance of the pollen-tube before they begin 

 to develop, and then take another year to ripen. 



Why should the pollen-tube always grow with its 

 end directly towards the very narrow opening by which 

 it is to enter the ovule ? 



For the ovule is often far away— what, considering 

 the size of the pollen-grain, may be called, without 

 exaggeration, hundreds of miles away — while the door 

 by which alone the tube can find entrance is the 

 merest point. Indeed, the ovules themselves are often 

 mere specks, and usually they are placed in what looks 

 Hke r most inaccessible position, quite enclosed in the 

 ovary. Often, too, there are hundreds, and even 

 thousands, of ovules in one ovary, each of which 

 receives at least one pollen-tube, in some cases more. 



Even when it has taken the first turn downwards 

 in the right direction there is plenty of room— either 

 on its way down the pistil stalk or when it reaches the 

 ovary— for the tube to go astray. But instead of doing 

 so it makes unerringly for its mark, and we can only 

 conclude that some definite arrangements exist by which 

 it is directed into, and kept in, the right way. 



