206 Lake Maxinkiickee, Physical and Biological Survey 



few scattered small patches on the west side of the lake. It also 

 grew along shore south of Green's. 



These hillside plants were fairly large (about 4 feet high) but 

 did not attain the immense size recorded for the species — 8 to 10 

 feet high and an inch in diameter. These gigantic forms are to 

 -be found in the rich black mud along the Missouri River. 



This horsetail presents much the same appearance all the year 

 round, except that it is a brighter green during the summer months 

 and becomes a brownish green during the winter. Cones of fruit 

 can be found on the apices of some of the stems the whole year 

 round. Growth takes place at the nodes in the portion covered by 

 the sheath and during the growing season the plants can be easily 

 pulled apart at the joints, but during the winter these parts harden 

 and it is difficult to pull the plant apart. 



In late autumn the hollow joints are filled with water, which 

 runs out copiously upon pulling the joints apart. This freezes into 

 a solid core of ice during the winter, but does not burst the stems. 



Along the Yellow River near Plymouth in 1909, a peculiar spec- 

 tacle was exhibited by a patch of these plants which had been coated 

 by mud during the early part of the year, while the river was in 

 flood. The plants had grown considerably afterward and displayed 

 alternating bands of yellow where coated with clay, and green, 

 the new growth. By completely staining these plants at various 

 intervals, fruitful studies could be made concerning the rate of 

 growth. 



This plant contains an abundance of silex in its composition, so 

 much that it has been used for scouring utensils. By soaking the 

 plants in a mixture of aqua regia, which dissolves out everything 

 but silex and cellulose, and then by soaking the remaining portions 

 in cupro-ammonia, produced by placing copper filings in ammonia, 

 to remove the cellulose, delicate glass skeletons can be formed. 

 Even the guard-cells of the stomata are silicified. 



When these plants are decapitated they frequently put out 

 slender branches. 



23. SMOOTH SCOURING-RUSH 



EQUISETUM LAEVIGATUM A. Br. 



This species, which was not very common about the lake, is 

 smaller and smoother than the preceding. It grew along the rail- 

 road near the lake, and some was found in fruit June 20, 1901. 

 There was also a thick patch on the hillside south of the Plank 

 cottage on Long Point. 



