THE FAMILIES, GENERA AND SI E^IEJ OF PTERIDOPHYTA. 477 



I' amily IX .—MA RSI LI A CE.-E. 



Vernation circinate. Sporangia contained in sporocarps, 

 each of which is the equivalent of a leaf-segment and encloses 

 several sori, the latter composed both of micro- and mega- 

 sporangia. Each spore is furnished with an epispore of 

 hardened frothy mucilage. — The spores pass the dry season in- 

 side the sporangia. The mature plant is aquatic or amphibious,, 

 and has a thin, creeping, much-branched stem, bearing leaves- 

 at distinct nodes ; roots are formed from the lower side of the 

 stem. 



I. Marsilia, Linn. 



Spores of Ijoth kinds contained in the same receptacle, which 

 is placed at or near the base of the long petioles. Leaves 4- 

 foliolate. — In habit and appearance these plants nearly resemble 

 a 4-leaved clover; said to be readily eaten bv cattle. 

 Leaflets i to 2 lines long, h line broad, slightly emar- 



ginate at point, villose; rhizome short ... i. Burchcllii. 

 Leaflets 2 to 6 lines long, cuneate, divided about half- 

 way into two linear lobes: rhizome wide, creeping. 



2. biloha. 

 Leaflets g lines long and broad, with a broadly cuneate 

 base, and rounded, crenate or occasionally emargin- 

 ate outer edge 3. macro car pa. 



1. M. Burchcllii. A.Br. — Marshes or vleis: often persisting" 

 on the dry ground. "Transvaal" teste Baker. 



2. M. biloba, W'illd. — Vereeniging, H., Burtt-Davy. 



3. M. luacrocarpa. Presl. — Pretoria. Pa., Rchmann; Potchef- 

 stroom, Pm.. along the Mooi River and water furrows, Burtt- 

 Dai'v 1,027; Rapetsi, Ze., 4,000 ft., SchJcchtcr. 



var. nov.. Springbok Flats, Wg., common in vleis, Burtt- 

 Davy. 1,746. 



Class II.— EQUISETALES ( Morset.uls). 



Homosporous (some fossil forms are heterosporous), with 

 dioecious prothalli. Sporangia situated on specially modified. 

 peltate (shield-like) leaves (sporophylls), which are closely 

 packed together and form a cone. Cone borne terminally, 

 limiting the growth of the shoot. Sporangia developed from 

 a large group of epidermal cells, the archesporium being uni- 

 cellular. — Stems much branched; internodes jointed; branches 

 arranged in whorls, developing acropetally. Leaves small in 

 comparison with tlie stem; arranged in whorls and united to 

 form a sheath; not green. 



Only family ' X. EQUISETACE^. 



Family X.—EQUISETACE.E (Horsetails). 



Sporophylls free, shield-like, each having a short stalk bear- 

 ing usually a hexagonal plate and closely compressed into a 

 cone. Sporangia situated on the underside of the sporophylls, 

 one at each angle, sac-like, opening inwardly bv a longitudinal 

 cleft ; ring absent. 



