106 ISOBTACEAE. [ [soetes. 
Family V. ISOETACEAE. 
Aquatic or amphibious perennials, often entirely submerged, rarely 
terrestrial. Stem (corm) short and tuberous, of firm texture, 2-3-lobed ; 
roots numerous, rather fleshy, dichotomously forked, springing from the 
furrows of the stem. Leaves many, forming a dense tuft at the top of the 
stem, linear or filiform, flat in front, rounded at the back, dilated and sheathing 
at the base, always furnished with 4 longitudinal air-channels divided by 
transverse partitions, and with a single central vascular bundle ; stomata 
present, or absent in those species which are permanently submerged, 
Sporangia large, membranous, placed in a hollow (fovea) of the dilated base 
of the leaf and sometimes partly concealed by the membranous margin 
(velum or indusium) of the fovea, 1-celled, but often imperfectly divided 
by rods or plates of tissue (trabeculae), those of the outer leaves containing 
macrospores, those of the inner leaves microspores. Immediately above 
the fovea is a flattened membranous plate called the ligule. Macrospores 
large, globose, usually chalky-white, with three ribs radiating from the 
apex. Microspores very minute, trigonous. 
A very isolated family, consisting of the single genus Isoeies, allied on the one 
hand to the Lycopods and on the other to ferns. In germination a male prothallium 
with a single antheridium containing spermatozoids is developed within the microspore, 
the spermatozoids being set free by the bursting of the coats of the microspores. The 
macrospores in a similar manner each produce a female prothallium bearing 2 or 3 
archegonia, which are ultimately exposed by the splitting of the macrospore along the 
three ridges. Fertilization then takes place in the same way as in ferns. 
1. ISOETES Linn. 
Characters of the order. 
Widely distributed in most temperate and tropical regions. Over 60 species are 
admitted in the most recent enumeration, but many of them are very imperfectly known. 
The two found in New Zealand are endemic. 
Macrospores tubercled .. + 23 i =f .. iL. I. Korku. 
Macrospores smooth a +) ++ i> +. .. 2. I, alpinus. 
1. I. Kirkii A. Brawn in Berl. Monatber., July, 1869—Permanently 
submerged. Stem short, tuberous, deeply 3-lobed; roots numerous. 
Leaves 10-30, very slender, 3-12in. long, about s'gin. diam., tapering to 
a fine point, pale-green, diaphanous, usually with a few stomata, but with 
no accessory bast-bundles. Sporangia rather small, broadly oblong er almost 
elobose, about din. long; indusium complete. Macrdspores rather small, 
chalky-white, beset all over with small unequal tuberclés. Microspdres 
very minute, trigonous, most minutely punctate——T7. Kirk in Trans. N.Z. 
Inst. ii (1870) 107, t. 7; Bak. Fern Allies (1887) 127; Thoms. N.Z. Ferns 
(1882) 109; Cheesem. Man. N.Z. Fl. (1906) 1043. 
Nort Isutanp: Wairua River, A. Thompson! lakes in the Middle Waikato basin, 
abundant, 7. Kirk! T. F. C.; Lake Rotokakahi, 7’. Kirk! Lake Taupo, C. J. Norton! 
Sout Istanp: Small lakes near Lake Tekapo, 7’. F. C. Sea-level to 2500 ft. 
Best distinguished from the following species by its smaller size and more slender 
habit, fewer leaves, and particularly by the conspicuously tubercled macrospores. 
2. I. alpinus 7. Kirk in Trans. N.Z. Inst. vii (1875) 377, t, 25.— 
Permanently submerged ; much larger and stouter than J, Kirkii. Stem 
stout, deeply 3-lobed. Leaves very numerous, 30-70, 6-18 in. long or even 
