EQUISETUM. 
261 
above these the oblong-ovate blunt cone is seated on a 
bare stalk-like portion of the stem, one to two inches long. 
The stems are round, succulent, pale-coloured, with about 
twelve slender ridges and corresponding shallow furrows, 
nearly smooth, the siliceous particles which coat the sur- 
face being too minute to impart much roughness. The 
sheaths are large and loose, and are divided at the margin 
into three or four bluntish lobes ; their lower half or 
tubular portion is pale-green, their upper half or lobes 
bright-russet ; they have an equal number of ribs with the 
stem. The slender branches, which are deflexed, grow to 
about a couple of inches in length, and produce from their 
joints a series of secondary branches, which grow from 
about half an inch to an inch in length. The average 
height of the fertile stems is about one foot. 
The barren stems are more slender and less succulent 
than the others : they also produce more numerous whorls 
of branches. These grow from fifteen to eighteen inches 
high, and are ribbed like the others, only somewhat more 
prominently. The sheaths fit closer than those of the 
fertile stems, but in colour and in the division of their 
margin they resemble them exactly. The whorls of 
branches are very dense, being compoundly branched. 
