112 THE BRACKEN-FERN'. 



If good microtome sections of young sori can be had, study 

 and draw, showing the development of the sporangia, observ- 

 ing the following stages: 



6. The young stalk with cell divisions at right angles to its 

 long axis. 



7. An oblique division forming an apical cell. 



8. The primary wall cells surrounding the single archesporial 

 cell. 



9. Completed wall cells, surrounding sporogenous cells. 



10. Sporangia containing spore mother-cells, and others with 



spores. 

 V. THE GAMETOPHYTE AND SEXUAL REPRODUCTION. 



1. The gametophyte body. Examine the soil or brick upon 

 which spores were sown some three or four weeks pre- 

 viously. Observe: 



a. The green coating given by the young gametophytes 

 (prothallia) developing from the spores. Mount some 

 of the material and study the development of the 

 gametophyte, observing the following stages: 



b. Spores just beginning to germinate, showing the pro- 

 tonemal or filamentous structure, and the first rhizoid. 

 Draw. 



c. Specimens in which the filament begins to broaden by 



means of longitudinal and oblique cell-walls, as well as 

 by the transverse ones that first appeared. Such stages 

 should show the early appearance of the apical cell; 

 also the formation of rhizoids. Draw. 

 In material six to eight weeks old examine: 



d. Fully formed gametophytes, showing the characteristic 

 heart-shaped body, the deep apical notch, the rhizoids 

 on the under side of the dorsiventral body. Diagram 

 the body, and draw a few cells in detail. 



2. Sex organs and gametes. 

 a. Antheridia. 



