bordered with a ring of dark cells ; the bast is confined to a 

 small triangle on the keels, the green parenchyma being continu- 

 ous under the grooves, or in stout stems in mid-season bearing 

 one to several accessory bundles of bast ; secondary stems often 

 bearing vallecular holes, though often wanting carinal, the true 

 branches wanting both, the centrum being about 6-8 times as 

 broad as the thin walls. 



RANGE AND HABITAT. 



In common with all true Equiseta, with the sole exception 

 of U. Bogotense, which inhabits the cool regions of the Andes, 

 this species thrives in the cold temperate regions of the North- 

 ern Hemisphere, being found in America from Virginia to Nova 

 Scotia and Washington, northward to Alaska. It extends across 

 Eurasia in a belt of 15 degrees of latitude, usually common in the 

 northern, but rare in the southern part of its range. Usually 

 growing on a muddy bottom in a few inches of water, it is only 

 accidentally found in a soil that is not saturated. It reaches its 

 finest estate in New England in the partial shade of cedar 

 swamps, growing on the peaty tussocks, often 5 ft. high, 

 with branches reaching 8 inches in length. In low undrained 

 areas it grows in mud amongst tussocks Oi sedges, and in shal- 

 low pools of sluggish streams. It is usually cropped by cattle 

 where they have access to it. Under the above conditions the 

 mud is moderately firm and the plant well branched (verticil- 

 la turn), in deeper pools and looser mud it becomes crowded and 

 unbranched (limosum). Unwonted firmness in the soil, as where 

 sand or gravel has been deposited on* it by freshets, causes a 

 stunted branchless growth (uliginosum) . It may be found in all 

 its aspects on tidal flats near the mouth of rivers, above the 

 reach of salt water. Here often in company with E. litorale, it 

 covers large areas, either alone or mixed with other vegetation 

 of these localities. It is less common in pools of small streams, 

 being often absent from those emptying directly into salt water, 

 though abundant in all the ramifications of those emptying into 

 large rivers. This is doubtless because in the latter case the 

 plants have spread directly by root division, but contiguous 

 streams have not been stocked because it is so difficult for the 

 plant to spread by spores. 



