372 



Stems. — The longest stem of E. hyemale I could find measured 

 three feet two inches : it consisted of eighteen articulations. Several 

 other stems measured nearly three feet in length. The longest articu- 

 lation on any stem examined was about three and a half inches; occa- 

 sionally a very short internode occurs among the rest, and there are 

 sometimes two or three such in succession. 



The thickest stem I observed was, in various respects, peculiar. It 

 was composed of eleven principal articulations, the seventh of which, 

 broken by accident, was bent at about a right angle to the lower part 

 of the stem. The eleventh articulation was about one inch in length, 

 and in it was inserted a sort of double stem, or rather a couple of 

 stems, one of which, about one fourth the diameter of the original, 

 consisted of four short articulations, having about twenty striae, all 

 that remained of the other being the decayed basal sheath. The bro- 

 ken internode and sheath were wet with an orange-coloured liquid, 

 which, when touched, stained the hand. The cause seemed to be, 

 that rain had lodged in the sheath and spread itself over part of the 

 internode. Both, when dry, were partly quite black and partly of an 

 orange colour. Does this indicate the presence of iron in the plant ? 

 I have already mentioned the fact, that I generally find E. Mackaii 

 and E. variegatum in the vicinity of water impregnated with that 

 mineral. 



Another stem, growing in the river, had but five articulations, the 

 upper part having decayed. At the top of the fifth articulation there 

 were two opposite branches, the one upwards of thirteen inches long, 

 the other rather shorter, each having twelve articulations, besides the 

 black radical sheath. The sheaths of the main stem had fallen off, 

 and a few setiform black teeth were present on the upper and lower 

 sheaths of the two branches. 



The standard or normal number of striae both on this plant and on 

 the other two, appears not to depend either on the length or thickness 

 of the stem. The greatest number I have found on one of the most 

 luxuriant stems, but not the stoutest, is twenty-eight; the smallest 

 number, but not on the smallest stem, fourteen. On some of the most 

 slender stems 1 have counted twenty-one, which I consider the stan- 

 dard number. The striae diminish in breadth, but not generally in 

 number, as they approach the top of the stem, nor is the greatest num- 

 ber always found on the thickest internode. Taking an average stem 

 of each plant, E. hyemale appears to have the narrowest ridges; E. 

 Mackaii the widest ridges and narrowest furrows ; E. variegatum, 

 ridges and furrows of nearly equal width, and, if there is any differ- 



