348 EQUISETACE^:. [Pilularia. 



ORD. 93. MARSILEACE^. Br. Pepper-wort Family. 



Fructification of two kinds, enclosed in a one- or more- 

 celled involucre near the root. Aquatic plants of various re- 

 gions. 



1. ISOETES. Linn. Quill- wort. 



Involucres formed of the swollen base of the leaves, 1-celled. 

 Seeds angular, inserted upon many filiform receptacles. 

 Named from to-os-, equal or alike, and eros, the year ; or ever- 

 green. 



1. I. lacustris, Linn. European Quill-wort. Leaves subu- 

 late, bluntly 4-angular, of four longitudinal internally jointed 

 tubes. Br. Ft. ed. 3. p. 458. Hook, in Fl Lond. N. S. 

 t. 131. E. Fl. v. iv. p. 343. 



Bottoms of lakes. Upper Lough Bray, and in several lakes in Cun- 

 namara. A very singular aquatic ; its fructification being entirely 

 concealed at the base of the cellular, subulate leaves. " Mr. W. Wil- 

 son considers the fructifications to be of two kinds : in one the con- 

 tained granules are oval, pellucid, and with sutures : in the other they 

 are sphaerical, and splitting at the sutures into four portions (one por- 

 tion hemisphaerical, the other three triangular) and they are rough on 

 the surface." (Hook.) 



2. PILULARIA. Linn. Pill-wort. 



Involucres solitary, nearly sessile, globose, coriaceous, 4-celled : 

 each cell containing two different kinds of bodies ; (anthers ? 

 and pistils ?) Name ; pilula, a little pill, which its fructifi- 

 cations resemble. 



1. P. globulifera, Linn. Creeping Pill-wort. Br. Fl. ed. 3. 

 p. 458. E. Bot. t. 521. Hook, in Fl. Lond. N. S. t. 83. E. 

 Fl. v. iv. p. 342. 



Margins of lakes and pools, and in places that are partially overflowed. 

 Abundant in marshy ground about two miles from the mouth of the 

 Blackwater, near Lough Neagh ; Mr. J. Campbell. In a ditch by 

 the river Bann, a little below Jackson's Hall, Coleraine ; Mr. David 

 Moore. Stems creeping, long, and entangled. Leaves setaceous, 

 erect, two or three from one point, four to five inches long. Involucres 

 at the base of the leaves, about the si^e of small peas, brown, downy 

 on the outside. 



ORD. 94. EQUISETACE^E. Rich. Horse-tail Family. 

 Fructification terminal, in spikes or catkins, consisting of 



