84 



that we find all young flowers belonging to one cupula to be 

 of about the same size. (fig. 3. PI. II). After a while again it 

 is seen that the young flowers increase in size become fre- 

 quently laterally compressed at the base and that the yellow 

 cushion becomes smaller and smaller owing to the gradual 

 destruction of the paraphysal hairs by the growing, pushing 

 flowers. A little more growth still and the flowers are ready 

 to be fertilised. Very soon after pollination the impregnated 

 ones begin to grow faster than their less fortunate sisters and 

 can thus be distinguished from those which have not been 

 fertilised. 



To obtain the first stages of fertilisation it is necessary to 

 collect inflorescences like the one drawn in fig. 4 PI. II, where 

 with some routine the fertilised flowers can be distinguished 

 from the not fertilised ones. Flowers at this stage will show 

 the sprouting pollen on the top of the nucellus, the pollen- 

 tubes having grown downwards in the nucellar tissue over a 

 shorter or longer distance, while none of them have as yet 

 reached the embryosac. It is of course from this point onwards 

 that the collection of material for embryological research has 

 to begin. Before doing this it is however necessary to assure 

 one's self at some of the older inflorescences of the same tree 

 that flowers of this tree have been pollinated, for if fertilisa- 

 tion does not take place the flowers grow all the same and 

 gradually diff'erences as to size occur also, owing to the more 

 fortunate position some of them occupy in regard to the food 

 supply. Such apparently fertilised but in reality unfertilised in- 

 florescences can be distinguished generally from the fertilised 

 ones in as much as the non-pollinated inflorescences contain a 

 much larger percentage of apparently fertilised flowers than the 

 pollinated ones. 



This at first rather startling fact becomes very simple on a 

 little after thought. Owing to the scarcity of male trees men- 

 tioned allready in the introduction, fertilisation is always a 

 rare occurrence, so that generally but very few flowers of an 

 inflorescence are pollinated. As these few impregnated flowers 



