— 17— 



its favor, but the average of all stems seems to point to its close 

 alliance with hyemale. 



Length of Joints. — In all specimens I have seen, the first two 

 or three joints above the ground are shorter than the rest; in fact, 

 the joints continue to increase slightly until the middle of the 

 stem is reached. The fourth joint above ground is of about 

 average length and this was the one measured. 



Length of joint in inches and eighths, i in. x 5 6 7 2 in. 1 2 3 



53 Jolietsp 1 3 7 14 8 11 2 



76 Patterson sp o o o o 1 2 12 



104 Robustum sp o o o o 6 14 20 



4 5 6 7 3 in. 1 Av. 



6100 o o 2 z /i in. 

 14 16 18 10 2 2 iY% in. 

 36 17 ir o o o 2 T 3 6 in* 



From this it appears that the specimens of robustum average 

 slightly shorter in the joints than those of hyemale and notwith- 

 standing its number of small stems does not have so great a 

 range as hy.emale. The longest joint found in any part of 150 

 stems examined measured 3^ inches. 



X umber of Grooves. — One of the most important points in 

 distinguishing Equisetum species is the number of grooves in the 

 stem. From the following table it appears that while the ex- 

 tremes may be wide apart, the bulk of the stems vary but little : 



Number of Grooves. 19 20 21 22 23 24 25 



50 Joliet sp 1 o 1 1 1 3 4 



73 Patterson sp o o o 1 3 g 19 



no Robustum 4 9 13 10 10 10 12 



26 27 28 29 30 31 32 33 34 Av. 



'5 7 13 4 5 3 2 o o 27 X 



10 18 4630000 26X 



987422541 23 



The small number of grooves above noted for robustum is 

 clearly due to the small, perhaps secondary, stems. 



Sheaths. — The length of the sheath is practically unvarying. 

 In none of the specimens examined did they measure more than a 

 quarter of an inch or less than three-sixteenths. The width of 

 the sheath varied with the diameter of the stem, the longest 

 sheaths being always on the largest stems. 



