— 140° — 
datus vel deplanatus, albido-stramineus. Folia herbaceo-viri- 
dia, subtus pallidiora, in stipite inferne subhomoeomorpha, 
laminae lateralia subpostica, distantia (in ramulis subcon- 
tigua), ovato-oblonga (in ramulis angustiora), leviter falcata, 
obtusiuscula vel subacuta, latere anteriore inferne valde dila- 
tata rotundata albomarginata dense serrato-denticulata (in 
ramulis laxius paucidentata), versus apicem et toto margine 
posteriore integerrima, basi posteriore attenuata, nervo supra 
prominulo, subtus sulcato; axillaria lateralibus non majora, 
subaequilatera, utringue ad apicem usque serrato-denticulata; 
interimedia duplo-triplo minora, convergentia, oblique ovata 
(in ramulis oblonga), cuspidata, basi oblique inserta subcor- 
data, margine serrato-denticulata (in ramulis paucidentata vel 
subintegerfima), dorso sulcarinata. Spicae graciles, ramulis 
multo angustiores, exacte quadrangulares. Bracteae sub- 
homoeomorphae, ovatae, breviter acuminatae ‚ marginatae, 
serrato- denticulatae. Microsporangia oblonga. Microsporae 
parvae, albidae, acute cristatae, reticulatae. 
Isoötes Tuckermani A. Br. Vegetatio aquatica submersa. 
Rhizoma parvum bilobum. Folia minus numerosa, plerumque 
recurva, tenera, media longitudine Imm. lata, versus apicem 
vix conspicue attenuata, teretiuscula, fasciculis fibrosis peri- 
pherieis carentia, sed stomatibus parce instructa. Vaginae 
margines aceurrentes angusti, hyalini. Sporangium minutum, 
velo ad medium fere tectum, pallidum, collulis epidermidis 
sclerenchymaticis aureo-fuscescentibus raris et sparsis ornatum. 
Microsporae sublaeves vel vix conspicue tuberculatae. Macro- 
sporae 0,56 ad 0,66mm. erassae, inter angulos acute promi- 
nentes grosse et laxe rugatae, rugis elevatis varie erosis, a 
vertice radiatim excurrentibus, in faciebus vertieis subparal- 
lelis et parce anastomosantibus, in facie basali irregulariter 
subreticulatis. 
Isoötes Engelmanni A. Br. in Flora 1846 p. 178; Sillim. 
Journ 1847 p.53; Asa Gray Man. ed. IV. p. 606. Amphibia, 
emergens, Talids, plerumque polyphylla et longifolia. Rhizoma 
crassum, bisuleum. Foliorum vagina squamiformis plerumque 
elongata et pallida, marginibus acceurrentibus hyalinis; lamina 
utrinque plus minus evidenter marginata, antice planiuscula, 
dorso valde convexa, fasciculis fibrosis periphericis 4 (acces- 
sorüis nullis) percursa, stomatibus instructa. Velum angustum, 
decurrens. Labium non productum, subexeisum. Lingula 
basi cordata, oblonga. Sporangium plerumque pallidum et 
cellulis sclerenchymatieis destitutum. Microsporae laeves vel 
tuberculis parum conspieuis subdenticulatae. Macrosporae 
albae, 0,48—0,58 crassae, inter angulos rugis elevatis irregu- 
lariter dentatis favoso-retieulatae, 
