120 SOUTH AFRICAN BOTANY 
MALE CELLS or GAMETES. The vegetative cell bursts 
through the exine, and grows out into a pollen tube 
(fig. 72). This pollen tube grows down the style into 
the ovary, and the two male cells pass down it. At first 
the pollen grain ig nourished by the sticky fluid on the 
stigma, afterwards by the tissues of the style. 
83. Fertilization.—-When the pollen tube reaches the 
ovary it is guided towards an ovule, and enters it by the 
Micropyle. It pierces the apex of the nucellus, and 
the synergidae cause the apex of the pollen tube to swell 
and burst. One male cell then fuses with the oosphere. 
This is fertilization, and the fertilized oosphere is then 
called an Oospore, and finally develops into the Em- 
BYRO of the young seed. The other male cell fuses with 
the secondary nucleus, forming the endosperm nucleus 
This divides and forms the EnpospERM of the seed. 
PRACTICAL WORK. 
1. Examine the pollen grains of several flowers under the 
microscope, and if possible obtain a stigma in which pollen grains 
are germinating and examine it (Escholtzia is a good flower for 
this purpose). 
2. Put a drop of sugar solution on a slide, place some pollen 
grains in it—these will then germinate and the process can be 
observed under the microscope. , 
3. Cut sections through the ovaries of various flowers. In 
some of these it will be possible to make out the structure of the 
ovule. ° 
4, Examine and draw the Male and Female flower of Pump- 
kin, Begonia, Oak and Willow. 
5, Examine and sketch old and young flowers of Geranium, 
Salvia, Delphinium, Lupin, Oxalis and Primula. Examine also 
the inflorescence of Helianthus and sketch the florets in the 
various stages, 
