Fig. 4. Apparatus used in crossing flowers. 
Fig. 5. Pollination and fertilization in the rock-rose. 1. A single flower. 
2. A flower stripped of its outer whorls, showing a longitudinal section of the 
pistil and the thread-like pollen-tubes growing down into the ovules or seed- 
producing organs. 3. Enlarged view of upper part of pistil, showing the germ- 
inating pollen grains. 4. A single pollen grain, much enlarged. 5. A single 
germinated pollen grain. 6. A single ovule. All figures except (1) enlarged. 
(After Kerner and Oliver.) 
