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STRUCTURE 53 
or will demonstrate the function of the pollen tubes after 
you have completed the study of the ovary. 
Make cross sections of a young ovary and study 
them under the low power. How many chambers does 
the ovary contain? If it contains more than one it is 
a compound ovary and each chamber represents a sim- 
ple ovary. Note the approximately spherical bodies 
(ovules) in the chambers. To which part of the cham- 
bers are they attached? How many are there in each 
chamber? In order to ascertain this and the form of the 
chambers, break open some of the oldest ovaries you 
can get. The stem-like structures by means of which 
an ovule is attached is called the funiculus, and the point 
of attachment between the ovule and the funiculus, the 
chalaza. Draw in outline a cross section of an ovary 
showing the ovules. Into what do the ovules develop? 
An ovule is composed of a central mass, the 
nucellus, which is nearly surrounded by an integument 
composed of one or more layers of cells. Cut very thin 
cross-sections of an ovary taken from an unopened bud 
of Trillium, lily, or Canna, also ask the instructor for par- 
affin sections, which you will mount as directed. Carefully 
work out the structure of an ovule. Of how many layers 
is the integument composed? Note the opening into it, 
the micropyle. Try to work out the cell structure of the 
nucellus. Draw an ovule as seen under the high power 
as nearly accurate as possible. 
By means of two diagrams show the relation in 
position between the floral organs. Refer to Ganong’s 
Teaching Botanist, page 229, for a model of such dia- 
grams. 
