18 99. EQUISETTJM. 1. HIPPOCHAETE. 



simple or irregularly branched; branches solitary or in groups of 23, 

 rarely 4 5, simple or slightly branched again; ribs 6 30 or more, con- 

 vex, not rarely much narrower than the grooves^ smooth or roughish 

 (transversely and finely rugulose or furnished with a row of very minute 

 pustules) ; grooves provided with 2 separate series of stomata (each series 

 consisting of 1 line of pores). Sheaths often tight and tubular, or some- 

 what funnel-shaped, short or more or less elongated, the teeth persistent, 

 or deciduous with a persistent, truncate, rounded or triangular base and 

 then the mouth of the sheaths finally subentire, repand or serrate ; ribs 

 rather flattened at least towards the apex, angular and often acutely 

 margined on each side, provided with a vaulted, prominent central ridge 

 passing gradually into a rib of the stem in the lower part and disappearing 

 towards the apex. Spikes to 2 1 /* cm. long, acute or apiculate. 

 Br. India and Ceylon eastwards to Fiji. 



