SEEDS. 11 



nus), thistle, dandelion, wild lettuce, cotton grass {^Erio- 

 phorum). 



In the air of a still room see whether any of these fall 

 perpendicularly from a height of a few feet. What is the 

 case when the air is disturbed by fanning ? 



III. Examine the fruits belonging to some or all of the 

 following genera : Agrimonia, Geum, Desmodium, Circsea, 

 Galium, Lappa, Xanthium, Echinospermum, Cynoglossum, 

 Bidens, Cenchrus. 



Describe the various appendages and compare them as 

 to their efficiency. 



By means of a thread suspend weights to one of the 

 hooked appendages of the burdock and ascertain how 

 great a weight the hook will bear. 



IV. Write out a list of fruits attractive to animals, 

 taking care to include only such as you have yourself 

 observed. 



V. Discuss any other arrangements for dispersal of seeds 

 with which you are familiar. Read one or more of the 

 references given below.^ 



RELATIONSHIPS INDICATED BY SEEDS. 



I. Examine seeds of mustard, radish, cabbage, and 

 other cruciferous plants, comparing them with reference 

 to their form and size, form and position of the embryo, 

 nature of reserve material, and other points of difference 

 and resemblance. The study will be facilitated by com- 

 paring seeds that have been planted two or three days. 



"■ Darwin, Origin of Species, Chap. XII ; Lyell, Principles of Geology., 

 Vol. II, Chap. XL; Hill, Am. Nat, 1883, pp. 811, 1028; Hildebrand, 

 Verhreitu ngsmittel der Pflanzen ; Wallace, Darwinism. 



