2 
Ol)e Slower (Brower 
January, 1919 
Hybridizing and Crossing the French Iris. 
(Reprinted by permission from Horticulture, Boston.) 
By William Rollins. 
DESCRIPTION OF THE PARTS OF 
AN IRIS FLOWER USED 
IN HYBRIDIZING. 
fertilization, as each division 
of one pod contained fifty 
plump seeds. Figure 3 is a 
picture of an Iris flower with 
part of the wall of one section 
of the three celled ovary cut 
away to show the ovules, 
which are the small white 
dots. When their contained 
female cells are fertilized, the 
ovules become seeds. The 
ovary grows and becomes the 
seed pod. 
HOW TO HYBRIDIZE. 
The only instrument needed 
is a pair of strong tweezers. 
To buy one of the elaborate 
cases of instruments offered 
for sale is a waste of money. 
The sharp points of the twee- 
zers should be rounded and 
polished, to prevent them from 
wounding the delicate tissues 
of the stigmas, in removing 
the anthers from the flowers, 
to be used as females. Even 
a slight abrasion, like that in- 
tentionally made to the stigma, 
in Figure 6, might result in 
imperi. . .crtilization. 
FIRST STEP. 
Iris Athena. 
Figure 1 
other part of immediate importance to the 
hybridizer is the ovary with its ovules. The 
former is marked O in the cuts. It is gen- 
erally green, and not a part of what we 
usually think of as the flower. The ovary 
has three divisions, each connected with a 
stigma. The terms given are the old ones, 
but perfectly legitimate. To 
have used the modern ones 
would have complicated 
the description. They are 
long and would have needed 
microphotographs to ex- 
plain them. The pollen 
grains, strictly speaking, 
are not the male organs, 
or the ovules the female, 
they are only groups of 
cells containing them. 
For the purpose of cross- 
ing we may look upon an 
Iris flower as an apartment 
house having three suites, 
each occupied by one 
couple. If we wish the 
seed pod to be symmetri- 
cal, like those shown in 
Figure 9, we must be sure 
each family has about the 
same number of children. 
To ensure this we must 
apply the pollen to each 
stigma. The seed pods 
shown came from a plant, 
one of whose flowers is 
seen in Figure 1. They 
show good pollination and 
Every pleasant morning dur- 
ing the flowering season, walk 
between the rows of the va- 
rieties to be used as mothers, 
examining each plant to see 
which buds have begun to 
open enough to allow the tips 
of the drooping segments of 
the perianth to be grasped by. 
the tweezers and broken off 
at the base, revealing the anthers A, which 
are then to be removed in the manner in- 
dicated in Figure 6. One blade of the 
tweezers is to be slipped behind the tip of the 
anther and carefully slid down to the posi- 
tion shown, then close the blades and re- 
move the anther by drawing it away from 
the stigma. Repeat the process with the other 
two anthers. It is not safe to wait for the 
flower to open before removing the anthers 
as their pollen sacs may have burst, free- 
ing the pollen grains. Insects may bring 
these in contact with the sensitive surfaces 
of the stigmas. When this has occurred and 
the flower afterwards pollinated with the 
chosen pollen, the record kept of the cross- 
ing will be unreliable. The surface of the 
anther shown in Figure 4 is smooth, indicat- 
ing that the pollen is still within the sacs. 
When the erect segments of the perianth 
have expanded to the position in Figure 5 
the stigmas are ready to receive the pollen. 
The time in warm sunny weather is from 
two to three hours after the first indication 
of the opening of the flower, that is from the 
time when you should have removed the 
drooping segments and the stigmas. 
second step. 
Walk between the rows of plants, whose 
flowers are to be used as males, selecting as 
many blossoms of a kind as you have females 
of the variety you wish to cross with them. 
Examine the anthers to see that the pollen 
has come out of the sacs. You can tell this 
by the anthers having lost their smoothness, 
appearing granular, from the escaped pollen 
grains, which are now ripe. Place the 
selected flowers in a flat market basket, like 
the one in Figure 8, which should also hold 
We need know only a few 
terms to understand in a de- 
scription those parts of a 
flower used in crossing, but 
for the same reason a physi- 
cian should know anatomy a 
gardener should know the 
anatomy of plants. The more 
we know of plant physiology 
the better. At the end of this 
letter two or three interesting 
books to get acquainted with 
will be given as an appendix. 
The outer parts of an Iris 
flower are called the perianth. 
This consists of six segments. 
Three are upright or incurved. 
They are called the erect seg- 
ments of the perianth. Three 
are horizontal or hanging 
down. These are named the 
drooping segments ol the peri- 
anth. Within the floral en- 
velope thus formed are the 
male organs and parts of the 
female. The pollen, usually 
called the 'male agent, is con- 
tained in the anthers, indi- 
cated in the figures by the 
letter A. Those parts of what 
are usually called the female 
organs, which are enclosed in 
the perianth, are the stigmas 
marked in the pictures by the 
letters. Each stigma has two 
lips, shown by the letter L. 
The flower in figure 2 has 
had the drooping segments of 
the perianth removed, reveal- 
ing the three anthers A, and directly back 
of them, the three stigmas, S. The only 
♦The illustrations accompanying Mr Rollins’ series 
of articles on the Ins are so numbered that they do not 
arrange themselves correctly in the descriptive mat- 
ter. We call attention to this fact so that readers 
may understand why illustrations are referred to in 
the text which do not appear. They will all appear 
in good time, and will all be numbered so that in re- 
ferring to the articles as a series everything will be 
complete and plain. 
