PRACTICAL STUDY. 115 



the surface of the sand is rnoist sow upon it fern-spores provided 

 by the demonstrator. Cover the whole apparatus with a bell- 

 glass, and after three or four days remove some of the surface 

 layer of sand to a slide, add a drop of water, and examine with a 

 low po\ver. If none of the spores have burst, repeat the opera- 

 tion every week till some are found in germination. Follow this 

 process, making sketches of the different stages. 



4. PROTHALLIUM. 



Prothallia are common in most hot-houses, especially in the 

 fern-house. They grow on the sides and the soil of flower-pots, 

 on the earth under the benches, etc. 



a. Examine a prothallium with the naked eye or a hand- 



lens, then mount it in water and examine with your 

 lowest power. Sketch. 



b. Turn it over and sketch again. 



c. With your highest objective, study some of the mar- 



ginal cells, observing the protoplasm, chlorophyll- 

 bodies, etc. 



5. THE SEXUAL ORGANS. 



Find the cushion and search for the sexual organs. Observe 

 also the rhizoids and their superficial (epidermal) origin. 



a. Antheridia. Observe the size, shape, and contents of 

 antheridia of different ages, crush them, and observe 

 more carefully the mother-cells. If possible, find 

 moving spermatozoids. 



1). Archegonia. On the same or another prothallium 

 study the archegonia. Then cut sections of the 

 prothallium between pieces of moist cork or pith, 

 and make out the details of their structure. Stras- 

 burger recommends the piling of several prothallia 

 (carefully freed from sand) one upon another before 

 cutting, thus permitting a number of sections to be 

 cut at once. 



6. FERTILIZATION. 



This is not easy to observe, but the attempt may be made by 

 examining successively a number of very fresh prothallia in dif- 

 ferent stages. They must be mounted carefully (not flooded 

 with water), and are generally easier to observe after the specimen, 

 has been mounted a little while. 



