36 .PRELIMINARY STUDIES. 



Scrape off one of the sori upon a microscope slide and 

 examine under the low power of the compound micro- 

 scope. Notice the spores, which are borne in spore cases 

 or sporangia. 



3. We here meet with spores for the first time in 

 descending the scale of plant life. The Ferns and the 

 plants below them produce no seeds. Seeds, in the 

 higher plants, result from the fertilization of ovules by 

 pollen grains. Seeds grow directly into ordinary plants 

 when the conditions are favorable. Spores result from 

 cell division. They contain no embryo and do not grow 

 into ordinary plants. The alternation of generations is 

 very distinct in the Ferns. The ordinary Fern plants are 

 the sporophytes or plants producing spores. 



4. Spores grow by cell division. Sow Fern spores of 

 the previous year's production on sand and cover with 

 a bell jar. Keep moist and in a warm, light place, but 

 not in direct sunlight. Study the growth by cell division 

 by examining from time to time under the microscope, 

 both low and high powers, the green growth on the sand 

 that soon becomes just visible to the naked eye. These 

 growths are the protonemce. If the conditions are favor- 

 able, some of the protonemce will develop in six or eight 

 weeks into heart-shaped prothallia less than half an inch 

 in diameter. The prothallium is the gametophyte form 

 of the Fern, i.e., the form that bears male and female 

 cells which unite to produce again the sporophyte form or 

 the plant. The more minute study of the gametophyte 

 is best reserved for later work. It is well for the student 

 here to see the prothallium and to have his attention called 

 to the antheridia, or aggregations of cells which produce 

 the antherozoids, or minute male cells, the male gametes, 

 and to the aggregation of cells, the archegonia, that pro- 

 duce the oospheres, or female cells, the female gametes. 

 The male cells have the power of motion. At their ma- 



