REPRODUCTION 55 
thistle as soon as they are ripe? Has this any special sig- 
nificance ? 
How long do seeds of the locust usually remain in the 
pod? How are they set free? 
Why are not blackberry-seeds digested in the bodies of 
the birds which eat the berries? What relation does this 
have to seed-distribution? 
How do you account for the fact that young plants of 
the cherry, etc., so frequently appear along fence-rows ? 
How many kinds of agencies which you have proof of 
are used in seed distribution? Which seem most suc- 
cessful? 
In what ways may thorough seed distribution be of ad- 
vantage to the new plants? In case the parent plants are 
perennials, what advantage do they receive from seed-dis- 
tribution that annuals do not? 
By counting the seeds in one cone, pod, or head, as the 
case may be, and by approximating the number of such col- 
lections on an entire plant, estimate the number of seeds 
formed on one plant. Does a large percentage of these 
develop new plants? What becomes of those that do not 
form new plants? Is it a waste of energy for plants to form 
more seeds than those which are to develop into new plants? 
Explain. 
