SIZE OF OVULES 37 
ing the ovules shown in Figure 42 and those shown in Figure 38 
the number of ovules in a Tomato may be roughly estimated. 
An examination of the ovaries of many plants would show 
considerable variation in the number of locules and ovules, but 
in general, all ovaries consist of an ovary wall enclosing one or 
more locules which contain one or more ovules. 
Ovule. — Since ovules develop into seeds, they have the most 
to do with seed production and are, therefore, the most directly 
related to the function of the flower. The process of fertilization, 
one of the most important events in plant life, takes place in the 
ovule and a good understanding of fertilization requires a knowl- 
edge of the ovule. 
Size of Ovules and how their Number Compares with the Num- 
ber of Seeds. — Although ovules are the chief structures in per- 
forming the function of seed-production, in size they are usually 
very inconspicuous and not much can be learned 
about them without the aid of the microscope. 
In many plants the ovules are barely visible to I 
the unaided eye. When ovaries and ovules are 
shown in drawings, they are usually much en- _ 
larged, so that much more is shown than could _,/%6-, 4%: — Pistil 
gea, : : : : of the Tomato taken 
be seen by cutting sections and studying the from the flower and 
ovaries themselves, unless a microscope were drawn natural size. 
used. In Figure 48, the pistil of the Tomato is 
shown natural size. By comparing it with the pistil shown in 
Figure 42, it will be seen that in order to show the structures of 
the ovary, the pistil in the latter Figure is much enlarged. 
Since ovules are small, it is difficult to count them in ovaries 
where they are numerous. It is possible in many cases to make 
a rough estimate of the number of ovules by counting the seeds 
produced. Since each seed is a developed ovule, there must 
occur in the young ovary as many ovules as there are seeds in the 
mature ovary. From this it follows that those Tomatoes con- 
taining two hundred or more seeds must have had as many ovules 
in their young ovaries. 
Tf all the ovules became seeds then a count of the seeds would 
give the exact number of ovules; but in many cases, due to a lack 
of fertilization, space, or sufficient food supply, only a part of the 
ovules complete their development and become seeds. In Red 
Clover, as shown in Figure 40, there are two ovules, but when the 
