CHAPTER XXXV. 



OTHER FERN-LIKE PLANTS. 



THE HORSETAILS (CLASS EQUISETINE^E). 



526. General characters. The horsetails are very peculiar 

 plants, their form being so different from other living plants that 

 one would not suspect their relationship to the ferns were it not 

 for the method of spore production, and the characters of the 

 prothallium or gamete plant (gametophyte) . The stems possess 

 the chlorophyll and are green, with stomates in the epidermis, 

 while the leaves lack chlorophyll. The stems are marked with 

 longitudinal furrows and ridges which gives them a fluted appear- 

 ance. The stems in some species are branched, the branches 

 arising in whorls at the nodes. In other species the stems are 

 unbranched as in the scouring rush (Equisetum hyemale). Their 

 stems are well infiltrated with silica which makes them rigid 

 and rough, so that some, as the scouring rush, have been used to 

 polish certain metal work, and by country housewives for scour- 

 ing kitchen tables and floors. The stems are hollow except at 

 the nodes. The vascular bundles lie beneath the ridges and 

 there are long canals which lie underneath the furrows. There 

 is also an underground stem or root stock from which the aerial 

 stems arise. At the nodes are membranous sheaths which sur- 

 round the stem, and the upper edge of each one is toothed. These 

 sheaths represent the leaves; they are devoid of chlorophyll, photo- 



To THE TEACHER. In short courses or first-year courses in the high 

 school it may not be practicable to study any of the plants in this chapter. 

 At the discretion of the teacher preserved specimens may be used for illus- 

 tration. Horsetails, ciub mosses, etc., may be seen during excursions, and 

 the selaginellas can be seen in some greenhouses. Where more time is allotted 

 to the study or with more advanced students some of the examples described 

 in the text can be studied. 



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