IO CHARACEA AMERICANA, 
Nitellz flexilis Ag., Monarthrodactyle, Furcate, Homceophylla, Moncece, Gymno- 
carpe. Stem rather large, usually elongated (often two to three feet long), branched. 
Leaves mostly 6- rarely 7 to 8- verticillate (when more than 6 the extra ones are smaller), 
leaves 2-3 divided, rarely undivided, leaflets abruptly and minutely pointed. Anther- 
tdium apical, on the extremity of a leaf, subtended by two or three leaflets, or dy 
sporangtain place of the leaflets. Sporangia broad-oval or sub-globose when mature, 
with an evanescent coronula of ten hyaline cells, 1 to 3 in number, occupying the place of 
leaflets beneath the antheridium. 
Nucleus (ripe spore) oval, dark brown or black, wzth 7-8 strong and sharp angles 
on one side (a very important diagnostic mark), 0.40 -- 0.50 mm. long. 
This Nitella is quite common in flowing streams, or still water. It appears early in 
the season and often attains a large size (over three feet long). Though branching freely 
it has a loose habit, the branches and leaves mostly divergent. Color usually dark green, 
rarely pale. The fruit may be found from early in June (about New York) till late in July. 
Two marked forms are found, one with elongated stems and long leaves (_ forma elongata) 
representec| in thejplate; another not half the length or even a fewinches long but of 
a spreading habit ( forma brachyphylla). ‘The chief varieties (zzdéfica and crassa) are 
delineated in plate V. 
The most common form of fruiting is represented in fig. 3, one leaflet, and one sporan- 
gium occupying the place of the other leaflet ; next in frequency we find fig. 5, a fruiting 
leaf that normally carries 3 leaflets with no sporangium as in fig. 4: when two sporangia 
develop on the node of such a leaf the third leaflet is considerably shortened (fig. 6). 
Antheridia are commonly found in the forkings of sterile leaves or even within a verticill 
when they apparently occupy the place of a branch. It will be noticed that the exact 
reverse to the fruiting of Chara pertains in Nitella; in the former the antheridium occupies 
the place o' a bract (leaflet) and the sporangium is above it (or above “he bract in dicecious 
species); the sporangium representing a transformed shoot or branch. In Nitella, the 
sporangium zs zot axillary to a leaflet, and in scores of examples of JV. flexzlis we have 
never found two leaflets and also two sporangia at the same node, as represented in Sach’s 
Lehrbuch der Botantk. 
Two other species are found in America, belonging to the same section of Monarthro 
dactyle furcate homeeophylla moncecee, JV. acuminata A.Br. (possibly a sub-species of 
N. flexilis) characterized by the long-acuminate tips of the leaflets, contracted leaves and 
very small fruit. Dr. Engelmann has reported a var. sawbglomerata from Ill. (Mead) 
and forma brachyteles from St. Louis. 
The other species belongs to the glaeocarpz (fruit enveloped in mucus) JV. prelonga 
A.Br., a gigantic species, gathered by Dr. Ravenel in the Santee canal in 1851, sent by Dr. 
Engelmann to Prof. Braun and named by Prof. Braun; subsequertly found in Texas 
(Lindheimer) No. 753. (JV. gelatimosa A.Br., to which this has deen referred as a 
variety, belongs to the third general subdivision of the genus, Polyarthrodactyle.) 
Explanation of Plate IV. 
Fig. 1, plant natural 'size (forma elongata) ; 2, leaf terminating in two leaflets with 
an antheridium in the axil ; 3, a similar leaf with one leaflet and one sporangium ; 4, a leaf 
terminating in three leaflets with an antheridium in the axil ; 5, a similar leaf with two 
leaflets and one sporangium; 6, two sporangia and one leaflet ; 7, a ripe nucleus (spore) with 
8 sharp angles and furrows, caused by the enveloping cells of the sporangium. 
The leaflets have been somewhat shortened for lack of room; not= also that though both antheridia and sporangia are repre- 
ented of mature size, in reality the antheridia mature before the sporangia of the same node. 
