hydrocerusite 
hydrocerusite (hi-dro-ser'o-sit), . [< Gr. ;(%) 
(Mp-), water, + crrnsite, q. v.] A basic lead 
carbonate occurring in thin hexagonal plates. 
Hydrocharideae (hl"dro-ka-rid'e-e), n. pi. [< 
Hydroi'harix (-ill-) + -<'.] A natural order of 
inonocotyledonous aquatic herbs, with dioecious 
or polygamous regular flowers on scape-like 
peduncles from a spathe, and simple or double 
floral envelops, which in the fertile flowers are 
united into a tube, and cohere with the 1- to 3- 
celled ovary ; stamens 3 to 12, distinct or moiiii- 
delphous; stigmas 3 or 6; fruit ripening under 
water, indehisceut, and many-seeded. This, the 
frogbit family, embraces 14 genera anil about 40 species, 
which are widely distributed in the warm and temperate 
parts of the world, in ponds, lakes, and ditches. Also writ- 
ten //yi/rocAaracfce(Undley),//.i/drocAa)rce(Reichenbach), 
Iliiitrocharice (Dumortier), Hydrocharidacece (Ventant), 
and llifilrocharidince (Leunis). 
Hydrocharis(hi-drok'a-ris), n. [NL.(Linn83us), 
< Gr. iidpoxapK, delighting in water, < viup(vfip-), 
water, + x a 'P" v , delight, rejoice.] A genus of 
monocotyledonous plants, of the natural order 
Hydrocliaridcu', having floating stems, with 
floating tufts of radical leaves, peduncles, and 
submerged roots. The peduncles of the male plant are 
short, 2- or 3-flowered ; the female spathe is sessile among 
the leaves ; stamens 3 to 12 ; styles 6 with 2-cleft stigmas. 
H. Morsus-raruz, the frogbit> the only species, is dispersed 
over Europe and northern and central Asia. The form ap- 
pears to have been more abundant in Miocene times, four 
or live extinct species occurring in that formation in Eu- 
rope. 
Hydrochelidon (hi-dro-kel'i-don), n. [NL., < 
Gr. iidup (iitip-), water, + jc/taouv, a swallow.] A 
genus of Sterninaj, or terns, known as black terns 
or short-tailed sea-swallows. It contains several 
species of small size, with short and emarginate or mod- 
erately forked tail, very long and ample wings, and small 
feet with deeply emarginate webs. These birds undergo 
Common Black Tern {Hydrochelidon lari/ormis). 
changes of plumage unusual in the group, the adults be- 
ing chiefly black or blackish. There are several species, 
found in all parts of the world, such as the common black 
tern of Europe and America, //. lariformis, or fxeipes, or 
nigra ; the white-winged black tern, H. leucoptera ; and 
the whiskered black tern, H. hybrida. Boie, 1822. 
hydrochinon (hl-dro-ki'non), . Same as hy- 
droquinone. 
hydrqchlorate (hl-dro-klo'rat), . [< hydro- 
chloric + -ate 1 .] A salt of hydrochloric acid. 
hydrochloric (hl-dr6-kl6'rik), a. [< hydro(gen) 
T chlor(in) + -ic.] tertaining to or compound- 
ed of chlorin and hydrogen gas. Also chlorhy- 
dric, chlorohydric, cltlorydric Hydrochloric acid, 
HC1, a colorless gas having a suffocating odor and an acid 
taste. It is irrespirable, and not a supporter of combus- 
tion. It is extremely soluble in water, and its solution 
forms the hydrochloric acid or muriatic acid of commerce. 
It is one of the most important acids commercially, and 
is made as a by-product of the soda-ash manufacture. Its 
salts, the chlorids, are universally distributed in nature 
and extensively used in the arts. Also called hydrogen 
eWorld. Hydrochloric ether. Same as chloric ether 
(which see, under chloric). 
Hydrochceridae (hi-dro-ker'i-de), n.pl. [NL., 
< Hydrochcerus + -idce.~\ A family of hystrico- 
morphic rodents, represented by the genus Hy- 
drocluerus, related to the Caviida;, but distin- 
guished by certain cranial and dental charac- 
ters ; the capibaras or water-cavies. 
Hydrochcerus (hl-dro-ke'rus), n. [NL., < Gr. 
iidup (vSp-), water, +' x'P, a pig.] The typi- 
cal and only genus of HydrocJuerida?, common- 
ly referred to the Caviidte. There is but one 
species, H. capibara. See cut under capibara. 
Hydrochoreutes (hi"dro-ko-ro'tez), n. [NL. 
(Koch, 1837), < Gr. Map (tx'p-), water, + xP CVT 'K, 
a dancer, < x o P e i' elv , dance, < xPC, a dance : 
see chorus."] A notable genus of water-mites, 
of the family Hydrachnidas, They are parasitic upon 
water-bugs, as H. 'glolmlus upon Sepa cinerea, and their 
larva) have been found adhering to the eyes of the larva; 
of 
2935 
Hydrocorallinae (hi-dro-kor-a-ll'ne), n. pi. 
[NL., < Hydra (q. v.) + LL. oorattimtg, coral- 
line.] An order or suborder of Hydroidea, class 
llytlro:oa, resembling true corals, or corallige- 
nous Actinozoa, but belonging to a different 
class ; the coral-making hydroid hydrozoang, as 
millepores or milleporic corals. They have a hard 
coral-like polypary and two kinds of zooids, the ordinary 
nutritive gastrozooids and the mouthless tentacular forms 
known as dactylozoijids ; the comosarc consists of a net- 
work of anastomosing cells ; reproduction is by means of 
gonophores. The Hydrocorallinae include two families, 
Milleporida: and Stylasteridaf. 
hydrocoralline (hi-dro-kor'a-lin), . and w. 
I. o. Pertaining to the Hydrocorallina;, or hav- 
ing their characters ; milleporic. 
II. H. One of the Hydrocorallmce ; a mille- 
pore or some similar coral. 
Hydrocorax (hi-drok'o-raks), n. [NL., < Gr. 
Map (iifip-), water, + nopai;, a raven, crow.] 1. 
A genus of hornbills, of the family Bucero- 
tidai, in which Brisson (1760) placed all the 
species of hornbills known to him: restricted 
by late writers to the group of hornbills of the 
Philippines of which Buceros hydrocorax of Lin- 
nsBiis is the type, characterized by a flattened 
casque, chestnut-red and black plumage, and 
white tail. 2. A genus of cormorants, of the 
family I'lialacrocoracidce : a synonym of Phala- 
crocorax or Graculus. Vieillot, 1816. See cut 
under cormorant. 
Hydrocores (hl-drok'o-rez), n. pi. [NL., < Gr. 
vdap (Mp-), water, + nopif, a bug.] Same as 
Hydrocorisce. 
Hydrocorisae (hi-dro-kor'i-se), n. pi. [NL. (La- 
treille), irreg. < Gr. itoup (vdp-), water, + Kopif, a 
bug.] A division of heteropterous Hemiptera, 
embracing the aquatic species. They are charac- 
terized by having short antennae concealed in cavities be- 
neath the eyes, and natatorial legs. Called Cryptocerata 
by Douglass and Scott, and by Fallen distributed into two 
divisions. Also Hydrocores, Hydrocorisa. 
hydrocotarnia (hi"dro-ko-tar'ni-a), n. Same 
as hydrocotarnine. 
hydrocotarnine (Wdro-ko-tar'nin), n. [< hy- 
dro(gen) + cotarnine, q. v.] A crystalline al- 
kaloid (C^Hj^NOs) occurring in small amount 
in opium. 
Hydrocotyle (hl-dro-kot'i-le), n. [NL., < Gr. 
voup (iifip-), water, + KOTV^J/, a cavity, a cup. 
The plants grow in moist situations and the 
leaves are hollowed like cups.] A genus of 
plants of the natural order Umbelliferw, type of 
the tribe Hydrocotyleie, having the fruit much 
compressed, the calyx-teeth minute or obso- 
lete, the petals concave, valvate, or imbricate, 
and the umbels simple. About 70 species are known, 
very widely distributed over the warm and temperate 
parts of the world. They are usually small herbs, creep- 
ing and rooting at the nodes ; a few are erect. H. vulgaris 
(common pennywort, pennyrot, or flukewort) is a com- 
mon British plant, growing in boggy places and on the 
edges of lakes and rivulets. It has round peltate leaves, 
and small simple umbels of pale-pink flowers. There are 
hydrocinchonine (hl-drd-sing'ko-nin), n. [< 
lii/drodicn) + ciiHJtoiiiite, q. v.j An artificial al- 
kaloid (Cgof^fiNgO) derived from cinchonine, 
and differing from it in having two additional 
hydrogen atoms. 
hydrocoelia (hi-dro-se'li-a), . [< Gr. Map (Mp-), 
water, + noi'/ia, a hollow, the belly.] Inpathol., 
same as ascites. Thomas, Med. Diet. 
185 
Hydrocotyle Americana, 
a, flower ; 6, fruit ; c, same cut transversely ; rf, tuber. 
several American species, of which H. Americana and 
//. mnhellata are the most abundant, the former being 
common in the Northern States, and the latter from Mas- 
sachusetts south. //. Americana has recently been ob- 
served to produce tubers. (See cut.) H. mnacllata has 
sometimes been called ghfep's-bane, from its being sup- 
posed to cause foot-rot. H. Asiatica is employed in India 
as an alterative tonic, and the South African pennywort, 
//. mnttlla, is employed in dysentery. 
Hydrocotyleae (hi"dro-ko-tire-e), . pi. [NL. 
(A. P. de Candolle, 1830)', < Hydrocotyle + -eat."] 
A tribe of plants of the natural order Umbelli- 
fera; in which the fruit is laterally much com- 
pressed or with the commissures often narrowly 
constricted, the carpels acute or obtuse on the 
back. Also written Hydrocotylida; (Lindley), 
HydrocotyKne<v (Sprengel), and Hydrocotyleneai 
(Koch). 
hydrocranium (hi-dro-kra'ni-um), n. [NL., < 
Gr. Hap (vSp-), water, + upaviov, the skull, head.] 
Same as hydrocephaluti, 1. Dunylimm. 
hydrodynamometer 
hydrocuprite (hi-dro-ku'prit), . [< Gr. Map 
(i'<V>-), water, + citpriti; q. v.J A supposed hy= 
drated oxid of copper. 
hydrocyanic (hi"dro-si-an'ik), a. [< hydro(gen) 
+ eyan(ogcn) + -ic.~] In cltcm., pertaining to 
or derived from the combination of hydrogen 
and cyanogen Hydrocyanic acid, HCN, a color- 
less liquid which solidifies at 5" F. to feathery crystals, 
and boils at SO'. Its specific gravity is about 0.7. It dis- 
solves freely in water, forming a liquid which reddens 
litmus-paper but slightly. Laurel-leaves, bitter almonds, 
and many stone-fruits contain amygdalin, which under 
the action of a ferment breaks up into grape-sugar, oil of 
bitter almonds, and hydrocyanic acid. It is generally 
prepared by the action of sulphuric acid on potassium 
ferrocyanide. It is one of the most prompt and virulent 
poisons known. Very dilute hydrocyanic acid is frequently 
used medicinally as a powerful sedative and anti-irritant, 
especially to allay cough. Its salts are called cyanides, 
and some of them are of great commercial importance, 
particularly potassium cyanide and the complex cyanides, 
potassium ferrocyanide and f erricyanide. Msoprussic acid. 
hydrocyanide (hl-dro-si'a-nid or -nid), n. [< 
hydrocyanic + -ide^-.J A salt of hydrocyanic 
acid: same as cyanide. 
hydrocyanite (hl-dro-si'a-nlt), n. [< Gr. iifop 
(vSp-), water, + Kvav6f, blue, 4- -ite%: see cya- 
nite."] Anhydrous sulphate of copper in pale- 
green crystals, found at Vesuvius as a sublima- 
tion product of the eruption of October, 1868. 
When exposed to the air the crystals absorb 
water and become bright-blue. 
Hydrocyon (hl-dros'i-on), n. [NL. (orig. Hy- 
clrocynus, Cuvier, 1817) ; < Gr. Map (i>dp-), water, 
+ KVUV, dog. ] The typical genus of Hydrocyoni- 
nce. It includes African fresh-water fishes with 
elongated canine teeth, whence the name. 
Hydrocyoninae (hl-dro-si-o-ni'ne), . pi. [NL., 
< Hydrocyon + -ince."] A subfamily of fishes 
of the family Characinida:, typified by the ge- 
nus Hydrocyon . They have large conical teeth in both 
jaws; an adipose fln; a short dorsal flu; rather narrow 
gill-openings, the gill-membranes being grown to the isth- 
mus ; and the nasal openings close together. Species oc- 
cur in the fresh waters of both Africa and South America. 
hydrocyst (hi'dro-sist). n. [< Gr. vSup (Mp-), 
water, + Kvarif, a bladder (cyst).] One of the 
processes or tentacles attached to the coenosarc 
of the physophorous oceanic hydrozoans, borne 
with groups of gonophoreg upon a common 
stem, constituting a gonoblastidium or blasto- 
style. See cut under f/otioblastidmm. 
hydrocystic (hi-dro-sis'tik), a. [< hydrocyst + 
-ic.] Having the character of a hydrocyst. 
Hydrodictyeae (hi"dro-dik-ti'e-e), n. pi. [NL. 
(Kuetzing, 1843), < Hydrodictyon + -ece.] A 
subfamily of green-spored algw. typified by the 
genus Hydrodictyon. Also written Hydrodic- 
tyonece (Hassall), Hydrodictyonidece (Gray), and 
Hijdrodictietn (Mathew). 
Hydrodictyon (hi-dro-dik'ti-on), . [NL. (A. 
W . Roth, 1800), < Gr. Map (v6p-), water, + diK-vov, 
a net.] A genus of curious fresh-water algee, the 
type of the subfamily Hydrodictyece of the fam- 
ily Protococcacea: The individual cells are oblong-cy- 
lindrical and united into a reticulated saccate coenobium ; 
all are fertile ; some produce macrogonidia, which join 
themselves into a cosnobium within the mother-cell : oth- 
ers produce microgonidia, which are furnished with vi- 
bratile cilia and a lateral red spot ; these after a brief mo- 
tile period subside into protococcoid, thick-walled spores. 
(Cotike.) The plant when full-grown resembles a long purse, 
whence the name neater-net, and consists of a beautifully 
regular network of threads. The single known species, 
H. utriculatum, is common to North America and Europe. 
The Hydrodictyon may be looked upon as an elaborate 
type of a cell-family, one in which cells are conjoined 
in accordance with a definite plan, so as to make a body 
of definite shape and size, yet in which each cell is an in- 
dependent being, drawing nothing from its neighbors. 
H. C. Wood, Fresh-Water Algee, p. 93. 
hydrodynamic (hl"dro-di-nam'ik), a. [= F. 
hydrodynamiqtie, < Gr. iidap (Mp-), water, + 6v- 
va/us, power : see dynamic.'] Pertaining to or 
derived from the force or motion of a fluid ; re- 
lating to hydrodynamics. 
An important property of the harmonic nodal line, in- 
dicated by an interesting hydrodynamic theorem due to 
Uanklne, is that, when self -cutting at any point or points, 
the different branches make equal angles with one an- 
other round each point of section. 
Thomson and Tail, Nat. Phil., I. U. It 780. 
hydrodynamical (hi'dro-di-nam'i-kal), a. [< 
lii/<l>-f>(}yii<i>iiic + -fit.] Same as hydrodynamic. 
hydrodynamics (hl"dro-dl-nam'iks), . [PI. of 
iiydrodyiiriniic: see -!c\s.] The mathematical 
theory of the application of the principles of 
dynamics to fluids. As dtmamics is used in two senses, 
the wider to include the theories both of rest and of motion, 
the narrower to include only the theory of motion, there 
are two corresponding senses of the word hydrodynamics. 
See (tjtnainicx. Also called hydrokineticg. Equation of 
hydrodynamics. Sec gvoooo, 
hydrodynamometer (M-dro-di-na-mom'e-ter), 
n. [< Gr. vdoit(Mp-), water, + E. dynamometer.] 
