936 Borany. 
togamy). There are a good many plants, however, which 
have two forms of flowers, viz., large, showy, nectar-bear- 
ing, insect-pollinated ones, and small, inconspicuous self- 
pollinated ones, generally with a rudimentary perianth. 
Flowers exhibiting this form of autogamy are said to be 
cleistogamous. 
503. Examples are to be met: with-in some violets, wild 
touch-me-not, etc.: early in the season these have large 
flowers, which are pollinated by insects, but later only small 
cleistogamous ones appear, and in some violets these are 
subterranean. Without doubt it frequently happens that 
the pollen of wind- and insect-pollinated flowers falls upon 
their stigmas, resulting in accidental self-pollination; but 
too frequent a recurrence of this is guarded against by 
various structural devices. 
504. The foregoing are but afew of the general modifi- 
cations for securing proper pollination which flowers show; 
they must serve to direct the student’s attention to this 
interesting part of the study of plants, which can be taken 
up in connection with the writings of Darwin, Miller, 
Gray, and others. 
Practical Studies,—{a) Collect a few wild buttercup flowers. Begin 
at the lower side of the flower and carefully remove the five green 
sepals constituting the so-called calyx, next the five yellow petals 
constituting the so-called corolla, next the many stamens, and last 
the numerous small pistils which cover the rounded end of the floral 
stem. Make a careful drawing of a representative of each part. 
(6) Mount in water (after moistening with alcohol) a little of the 
pollen of the morning-glory, sunflower, mallow, and Indian corn. 
Note the surface markings. Crush the cells and test with iodine. 
Pollen-grains may be germinated by placing them in a five-per-cent 
solution of common sugar in water. The pollen-tubes may also be 
found by carefully mounting stigmas or longitudinal sections of stig- 
mas. Many grasses are good subjects for such studies. 
() Remove the pistil from a fresh pea-flower. Split it longitudi- 
nally, and observe that the ovules are in a row along one seam (suture). 
