HORSETAILS. 1 75 



some of these from the shoot. Note the short stalk ; how is this stalk at- 

 tached? Describe the sacs underneath. (These are the spore-cases.) 



Sketch a spore-bearing leaf. 



If some of the spores are at hand which fall out of the spore-cases when 

 the sporangia dry, examine them under a hand lens ; at the same time 

 breathe upon them. What happens ? 



286. The sterile shoot. Compare the sterile shoots with the fertile shoots. 

 Note the leaves arranged in the same way, but smaller. Note the branch- 

 ing of the plant and the arrangement of the branches. Are there leaves on 

 the branches ? Describe them. Sketch a sterile shoot. What is the color 

 of the sterile shoot ? In what part of the plant does the chlorophyll lie ? 

 In what part of the plant does the process of starch formation (or photo- 

 synthesis) take place ? ~ 



Compare the scouring rush (E. hyemale) if there is time. 



Demonstration 41. 



287. Spores and elaters. Mount some of the spores of equisetum on a 

 dry glass slip. Let each pupil examine them under the microscope, sketch 

 and describe the form ; breathe lightly on them and watch the result. 



288. The field equisetum. Fertile shoots. Fig. 150 repre- 

 sents the common horsetail (Equisetum arvense). It grows in 

 moist sandy or gravelly places, and the fruiting portion of the 

 plant (for this species is dimorphic), that is the portion which 

 bears the spores, appears above the ground early in the spring. 

 It is one of the first things to peep out of the recently frozen 

 ground. This fertile shoot of the plant does not form its 

 growth this early in the spring. Its development takes place 

 under the ground in the autumn, so that with the advent of 

 spring it pushes up without delay. This shoot is from 10 to 

 20 cm. high, and at quite regular intervals there are slight 

 enlargements, the nodes of the stem. The cylindrical portions 

 between the nodes are the internodes. If we examine the region 

 of the internodes carefully we note that there are thin mem- 

 branous scales, more or less triangular in outline, and connected 

 at their bases into a ring around the stem. Curious as it may 

 seem, these are the leaves of the horsetail. The stem, if we 

 examine it further, will be seen to possess numerous ridges 



