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of the upper tier elongate but little and form the crown-cells, which 
are however raised above the odsphere by the growth of the lower 
cells, and sometimes again divide by transverse walls, thus forming 
two superimposed rows, each of five cells. This is taken as the 
primary basis for dividing the Characeae into two subfamilies, the 
Chareae with five crown-cells and the Nitelleae with ten. These 
are further separated, the former into four and the latter into two 
genera, according to the relative positions of the antheridia and 
oégonia. Both genera of the Nitelleae, Witel/a and Tolypella, are 
well represented in North America, the latter perhaps attaining its 
best development here, though of the Chareae the typical genus 
Chara has alone been reported. 
Characeae are either monoecious or dioecious. In Chara the an- 
theridia are the terminal cells of metamorphosed leaflets, while the 
odgonia arise from the basal cells of the leaflets, on their upper side. 
In the monoecious species both kinds of organs are thus in close 
proximity to one another, except in a few where the antheridia and 
the odgonia are at different leaf-nodes though borne on the same 
plant. Inall cases the antheridia tend to develop first, and often fall 
off before the odspores mature; great caution must therefore be ex- 
ercised in calling species dioecious. After fertilization the odgonia 
increase greatly in size, owing to the growth of the oédspore and the 
enveloping cells; the resulting body is here called the sporocarp. 
The absence or presence of cortication, often a conspicuous fea- 
ture, was originally considered the chief distinction between the 
genera, but this has been found misleading. Cortication is never 
found except in the Chareae, but even in this subfamily many species 
are entirely uncorticated, one of these apparently having its closest re- 
lationships with one of the highest groups of Chara 
e development has long been known. On germination, the 
odspore divides transversely to its long axis into two cells, a larger 
which has no further function than to part with its contents to serve 
as food for the young plant, and a smaller which again divides into 
two by a wall parallel to the long axis of the spore. One of these 
two becomes the primary root. The other elongates and divides 
into a few cells, two of which become nodes, and from the lower 
of these a number of rhizoids are formed, The upper node divides 
into two cells, each of which separates off a superficial layer of cells. 
The first cell of the latter to be formed produces by its successive 
divisions the entire permanent plant, which thus obviously origi- 
