54 A LABORATORY MANUAL OF BOTANY 
the path of entrance? Is this of any advantage to the 
plant? 
Examine old and young specimens of the common mal- 
low. How do positions of stamens and carpels differ in 
flowers of different ages? At the time the anthers are ripe 
has the stigma developed its mucilaginous substance for 
holding pollen? Explain the advantage of these conditions 
to this plant. 
This study of pollination may be extended with profit 
if regions favorable for field-work are convenient. 
LESSON XXIX 
Reproduction—distribution of seeds 
Materials.—Seeds of pine, thistle, catalpa, dandelion, 
ironweed, fleabane, milkweed, cockle-bur, Spanish needle, 
beggar-tick, sand-bur; also acorns, beechnuts, fruits ‘of 
honey-locust, coffee-nut, hawthorn, and blackberry; speci- 
mens of tumbleweed, Russian thistle, and tumbling grasses, 
and the seed-pod of the water-lily. 
To. this list many specimens may be added in each 
locality. 
Observation and study.—There are so many plants try- 
ing to grow and to establish new plants over the surface 
of the earth that it is of great advantage to each to have its 
seeds germinate in favorable places. Numerous structures 
exist that aid in placing the seeds in regions distant from 
those in which the parent plants grow. 
Study the various seeds furnished and sketch, show- 
ing the structures which you think have to do with their 
distribution in each case. 
Examine the hooks of Spanish needles and cockle-burs 
under the microscope. 
Do the seeds fall from the tumbleweed and Russian 
