Theclum 
thyroid 
of Mosses which bear setae; 
The’cium, a layer of tissue below 
the epithecium, which contains 
the sporangia in Lichens (Minks), 
ef. EeitHecium, HyPporueEcium. 
The’in, the most important alkaloid 
in the leaves of Thea, the tea- 
plant. 
The’ke, sometimes used for the theca 
(ascus) of Lichens. 
theleph’oroid (Thelephorus, eldos, re- 
semblance), like the genus 7'hele- 
phorus. 
thele’phorus (477, a nipple, Popéw, 
I carry), covered with nipple-like 
prominences. 
thelotre’moid, having tubercular 
apothecia like those of Thelotrema. 
thelyg’enous (@7\vs, female, -yévos, 
race, offspring), inducing the 
female element, as ~ Castra’tion, 
the production of pistils in the 
male-flowers of a host by Ustzlago. 
Theobro’mine, the active principle of 
the cacao-bean, Theobroma Cacao, 
Linn. ; theobro’minus, the deep 
chocolate brown of the seed of the 
same plant. 
theoret’ic (@ewpytixds, speculative), 
pertaining to theory, as distinct 
from practice ; ~ Di’agram, a floral 
diagram of the theoretic com- 
ponents, not necessarily the same 
as seen on inspection. 
ther’mic (0épu7, heat), warm ; ~ Con’- 
stant, the sum of the mean tem- 
peratures of the days of active vege- 
tation, up to some definite phase 
in the plant’s life, minus a certain 
initial temperature determined by 
several years’ observations, and 
varying for the species (Oettinger) ; 
Ther’mo-cleistog’amy (+ CLEIsToG- 
AMY), when flowers do not expand 
as a consequence of insufficient 
warmth (Knuth); Thermotax’is 
(rdéts, order), changes produced 
by warmth; adj. thermotac’tic ; 
thermophilic (¢:Aéw, Ilove), applied 
to those bacteria which thrive in 
high temperatures; Thermot’onus 
(révos, strain), the relation between 
temperature and the manifestation 
270 
of irritability ; thermotrop’ic (rporn, 
a turning), relating to Thermot’- 
ropism, curvature dependent upon 
temperature (Wortmann). 
Thickening Lay’er, an apparent layer 
of cellulose on the inner face of 
a cell-wall; ~ Ring, Sanio’s term 
for a ring of meristem in which 
the first fibro-vascular bundles 
originate. 
Thigmot’ropism (@lyya, anything 
touched), curvature induced in 
climbing plants by the stimulus of 
a rough surface (Czapek) ; Thigmo- 
tax’is (rdaés, order) is a synonym; 
adj. thigmotac’tic. 
Thorn, usually an aborted branch, 
simple or branched. 
Thread, used by Blair for the Fina- 
MENT ; Thread-ind’icator, a form of 
apparatus for measuring the rate of 
growth ; thread-shaped, filiform. 
three-an’gled, trigonous; ~ cleft, 
trifid ; ~ cornered, ~ edged, with 
three sides, plain or incurved, and 
three acute angles, triquetrous; ~ 
leav’ed, trifoliate; ~ lobed, tri- 
lobed ; ~ wmnerved, with three 
principal veins; ~ parted, tri- 
partite; ~ ranked, with three 
vertical rows on a stem ; ~ ribbed, 
the midrib and one rib on each 
side more prominent than the rest; 
~ valved, trivalvate. 
thrice-digita’to-pin’nate, = TRITER- 
NATE. 
Throat, the orifice of a gamopetalous 
corolla or calyx, the fauces. 
Thrum (Grew), Thrumb (Blair), (1) 
the filament of a stamen, (2) in 
Composite florets, the anthers ; 
thrum-eyed, applied to a short- 
styled dimorphic flower, such as a 
primrose, the stamens alone being 
visible in the throat of the corolla. 
Thrush-fun’gus, the disease ascribed 
to Dermatium albicans, Laurens. 
Thun’der-broom = WIrTcHES’ BROOM. 
Thyll, Thyl’la, Thy'lose, Thy’llose 
(Germ. Thylle), cf. Tytoss. 
thy’roid (@upeds, a shield, edos, re- 
semblance), shield-like, peltiform 
(Heinig). 
