POLLINATION AND FERTILIZATION 117 
Many other flowers have interesting arrangements 
for pollination, e.g. Orchid, Lupin (and other Legumi- 
nosae), Violet, Protea, Campanula, Arum, Aristolochia. 
Some of these are described under their natural orders, 
but the student should observe as many as possible for 
himself—noting : (@) What insects visit the flower; (0) 
What arrangements the flower has for ensuring cross- 
pollination. 
79. Self-pollination.—A few plants are regularly self- 
pollinated, the commonest of these are Senecio and 
Capsella; other plants produce two kinds of flowers, the 
large showy ones, which are cross-pollinated, and small 
inconspicuous flowers, which do not open and which 
are self-pollinated. These are called CLEISTOGAMOUS 
flowers and are found in Viola, Oxalis and other plants. 
The cleistogamous flowers of Viola look like buds— 
their stamens contain very little pollen, and are closely 
pressed to the stigma. The poilen grains germinate 
inside the anthers. The petals are very minute. The 
production of these cleistogamous flowers ensures the 
setting of a fair amount of seed. 
80. Structure of the Ovule.---The ovule is attached to 
the ovary by a slender stalk, the Funichz. The body 
of the ovule consists of 4 mass of parenchymatous 
tissue, the NoceLius, with one large special cell, the 
EmMBRYO-SAc. 
Around the nucellus are two skins or INTEGUMENTS, 
but just opposite the embryo-sac these integuments are 
separated, and the space between is called the M1cro- 
PYLE. The base of the nucellus from which the in- 
teguments arise is called the CHALAZA. 
