366 
guished by the slit in the side of their embryo, their simple fruit, pendulous 
ovule, trisepalous calyx, and habit. 
Geography. Found commonly in the ditches and marshes of the northern 
parts of the world, but uncommon in tropical countries ; a species is found 
in St. Domingo, and another in New Holland. Two are described from equi- 
noctial America. 
Properties. Of little known use. The powdered flowers have been used 
as an application to ulcers. The pollen of Typha is inflammable, like that of 
Lycopodium, and is used as a substitute for it. De Candolle remarks that it is 
probable the facility of collecting this pollen is the real cause of its use, and 
that any other kind would do as well . 
GENERA. 
Typha, L. Sparganium, L. 
Alliance IV. FLUVIALES. 
Essential Character. — Floioers in loose spikes or solitary. 
Order CCLXIV. FLUVIALES, or NAIADACE.^. 
Naiades, Gen. 18. (1789) in part. — Fluviales, Vent. Tahl. 2. 80. (1799). — Pota- 
MOPHiL^, Rich. Anal. Fr. (1808). — Potamea:, Juss. Diet. Sc. Nat. 43. 93. (1826) ; 
DC. and Duby, 439. (1828). — Naiadea:, Agard Aph. 125. (1822). — Fluviales, 
Rich. Mim. Mus. 1. 364. (1815) ; Lindl. Synops. 248. (1829). — Hydrogetones, 
Link Handb. 1. 282. (1829). — Naiade.®, Ib. 1. 820. (1829). — Potamogetone®, 
Rchb. FI. Excurs. 1. 6. (1830). 
Essential Character. — Flowers hermaphrodite or unisexual. Perianth of 2 or 4 
pieces, often deciduous, rarely wanting. Stamens definite, hypogynous. Ovaries 1 or 
more, superior; stigma simple; ovule solitary, pendulous. Fruit dry, not opening, 1- 
celled, 1 -seeded. Seed pendulous ; albumen none ; embryo antitropous, with a lateral cleft 
for the emission of the plumule. — Water-plants. Leaves very cellular, with parallel veins. 
Flowers inconspicuous, usually arranged in terminal spikes. 
Affinities. In this order we have the nearest approach, except in Pistia- 
cese, to the division of flowerless plants. The perianth is reduced to a few im- 
perfect scales, and there is in some of the genera either a total absence of spi- 
ral vessels, or that form of tissue exists in a very rudimentary state. Pollini 
asserts, according to De Candolle {Org. Veg. 40), that spiral vessels do exist 
in them ; but Amici, on the other hand, maintains that there is no trace of 
them, at least in Caulinia. Ann. des Sc. 2. 42. The manifest affinity of Flu- 
viales to Juncaginacese determines a relation on the part of the former to Ara- 
ceae, which is confirmed by the tendency to produce a rudimentary spathe in 
some of them, and by their undoubted resemblance to Pistiacese, which may 
be understood as reduced Aracese. It is remarkable that Adanson was aware 
of this relationship between Aracese and Fluviales, to which, however, Jussieu, 
whose Naiades are a very heterogeneous assemblage, did not assent. They 
are generally translucent cellular plants, destitute of stomates, having no epi- 
dermoidal layer, and perishing rapidly upon exposure to air. Amici has seen 
the sap circulate in the transparent joints of Caulinia fragilis, which he states 
is the unknown plant upon which Corti made observations relating to the same 
subject. See Amici in Ann. des Sc. 4. 42. Agardh refers to this order both 
Ceratophyllum and Sparganium. 
