158 MORPHOLOGY AND LIFE HISTORY 



sporous, they give rise to dioecious gameto- 

 phytes. Are they, therefore, physiologically 

 alike? 



(g) Since the spores have different sex-value, some 

 giving rise to antheridial, others to archegonial 

 prothallia, suggest the advantage of the hygro- 

 scopic elaters in tending to tangle up together 

 several spores before they germinate. 



(h) Make drawings illustrating all points observed 

 under D, 2, (a)-(f). 



E. Sexual Reproduction: 



1. It is not essential in an introductory course to 

 study the gametophytes, and sexual reproduction 

 of Equisetum in the laboratory, and it is seldom 

 possible to secure suitable material in sufficient 

 quantity for a large class. 



2. If material is abundant and time permits, the 

 gametophytes may be studied, described, and 

 sketched, noting especially color and general form, 

 branching, rhizoids, archegonia, anther idia, and 

 the dioecious habit. 



3. From prepared slides further details as to arche- 

 gonia, antheridia, eggs, sperms, .and fertilization 

 may be studied, under the instructor's direction. 



F. Division of Physiological Labor: 



i. Write two or three paragraphs describing the 

 division of physiological labor, (a) as between 

 various vegetative processes, and (b) between the 

 latter and reproductive processes. Give special 

 attention in this to the work of each of the three 

 kinds of branches. 



G. Life Cycle: 



i. Make a diagram, as previously for other forms, 

 illustrating the life cycle of Equisetum. 



