156 BOTANY. 



ering it, the bud at the anterior end covered also with brown scales. Ob- 

 serve the numerous dark slender roots. 



Note the leaves, some of them perhaps plain (sterile) on the under side, 

 while others have numerous circular brown or blackish dots, the fruit dots 

 where the sporangia (spore-cases) and spores are borne. Describe the form 

 of the leaf. Name the different parts. Sketch the entire plant. Sketch a 

 portion of the under side of the spore-bearing leaf, to show the fruit dots. 

 Compare the polypody with several other species of ferns if possible. 



Exercise 53. 



258. The scattering of the spores. — If the study is made at a time when 

 the ferns with spores just ripe cannot be collected out doors, get some leaves 

 from greenhouses. Take those leaves where the fruit dots appear quite 

 black, and under the lens the sporangia appear like shiny rounded black 

 bodies. Place a leaf on white paper in a dry room, with the under side 

 uppermost. In the course of an hour or earlier watch for showers of spores 

 which are scattered around the leaf, Sometimes in a dry room these begin 

 to scatter in the course of a few minutes. The success of this exercise will 

 depend on the material being in the right condition. After a little experi- 

 ence in collecting it is not difficult to get the right material. 



Demonstration 38. 



259. To show the sporangia. — These can be shown from sporangia 

 which are just ripe, or from older material which has been dried, or pre- 

 served in formalin or alcohol. Scrape off a few of the sporangia from the 

 "fruit dot." Mount them in water for examination under the microscope. 



Let each student examine the form and structure. Sketch a sporan- 

 gium seen from the side. Name the different parts, the slender stalk, the 

 enlarged spore-case. In the spore-case make out a prominent row of cells 

 over the back and upper part (the annulus), note the "lip cells" in front, 

 one each side of the place where the sporangium opens. If there are any 

 spores in this preparation note and describe them ; sketch one also. If 

 there are none to be seen in the preparation made for the study of the 

 sporangium the teacher can mount some for study if desired. 



To see the snapping of the sporangium fresh ripe material may be 

 mounted in water ; then draw under the cover glass some glycerine and 

 watch the result. 



260. The Christmas fern. — One of the ferns which is very 

 common in the Northern States, and occurs in rocky banks and 

 woods, is the well-known Christmas fern (Aspidium acrosti- 



