402 
STRUCTURE AND LIFE HISTORIES 
chance, in the pollen-chamber of the ovules on neigh- 
boring female plants. The transfer of pollen to the female 
plant is pollination. 
359. Germination of the Pollen-grain. In the pollen- 
chamber the conditions favor the germination of the 
FIG. 299. Cycas revoluta. a, Pollen grains at shedding stage; X 500; 
b, later stage, showing prothallial cell (p) and generative cell (g), the tube- 
nucleus not shown; X 200; c, generative cell divided, giving rise to stalk- 
and body-cells; X 500; d, the stalk-cell-nucleus (s) being crowded out, 
and blepharoplasts appearing in the body cell (b) ; X 500; e, the body-cell 
shortly before division, showing two well-developed blepharoplasts; X 750; 
/, the two male cells resulting from the division of the body-cell; the beaks 
of the nuclei are attached to the cilia-bearing bands ;X 200. Reduced 
about two-thirds in reproduction. (After Ikeno.) 
pollen. This is also a new feature in life history. In ger- 
mination the pollen-grain develops absorbing organs 
(haustoria), which penetrate the tissue of the nucellar-cap 
(Fig. 300), and also larger tubes which carry the generative 
cell further down into the pollen-chamber. As the tube 
