porrect 
preventitious 
porrect’, porrec’tus ( Lat., stretched 
out), directed outward and for- 
ward; ¢f. ARRECT. 
por’ulus (Lat.), somewhat porous. 
Por’us = Pore. 
positive, the absolute or effective 
condition, opposed to negative, and 
prefixed for emphasis to such terms 
as Geotropism, Heliotropism, Hy- 
drotropism, etc. 
poste’rior (Lat., coming after), (1) 
next or towards the main axis, 
superior ; the reverse of ANTERIOR ; 
(2) in anthers = EXTRORSE; pos- 
ti’cal, posti’cous, osti’cus (Lat., 
that which is behind), on the pos- 
terior side, next the axis ; extrorse; 
Spruce and others use ‘‘ postical” 
for the ventral or rooting face of 
the stem of Hepaticae. 
postventit’ious, -tiws ( post,after,venio, 
I come), applied to growths which 
arise subsequent to their normal 
time ; ¢f. PREVENTITIOUS, 
poten’tial (potentia, force), existing in 
possibility, not in action; used in 
opposition to KINETIC; ~ Gam’eto- 
phyte, one which is functionally 
asexual; ~ Par’asite, w sapro- 
phyte which can live equally as 
a parasite; ~ Sap’rophyte, a para- 
site capable of existing as a sapro- 
hy te. 
Potetom’eter (roris, a drink, uérpov, a 
measure), apparatus for measuring 
the amount of water given off by 
the leaves of plants (Moll); Poto- 
meter, a similar instrument for 
measuring the flow of liquids in 
tissues (I. Darwin). 
pott’ioid (eldos, likeness), resembling 
the genus Pottia. 
Pouch = SILICLE; ~ shaped, hollow 
and bag-like, as the spur in many 
Orchids ; diges’tive ~ ; used by Van 
Tieghem and Douliot for the root- 
cap of the lateral roots of Legum- 
inosae and Cucurbitaceae. 
pow’dery, covered with a fine bloom, 
as the leaves of Primula farinosa, 
Linn. 
prae-, or pre- (prae, before), expresses 
priority in time or place. 
prae’cox (Lat., early ripe), appearing 
or developing early ; precocious. 
Praeflora'tion (praefloratio, blossom- 
ing before time) = AESTIVATION. 
Praefolia’tion (prae, before, folium, a 
leaf) = VERNATION. 
prae’morse, praemor’ sus (Lat., bitten 
at the end), as though the end were 
bitten off. 
praero’sus (Lat.), apparently gnawed 
off. 
praeus’tus (Lat., burned at the end), 
looking as if scorched. 
pras‘inous, pras’inus (Lat.), grass- 
green, leek-green. 
pra‘tal (pratum, a meadow), H. C. 
Watson’s term for those plants 
which grow in meadows or luxu- 
riant herbage; praten’sis (Lat.), 
growing in meadows, or pertaining 
thereto. 
precator’ius(Lat., relating to petition- 
ing), used for a rosary, as the seeds 
of Abrus; ~ contex’tus, necklace- 
shaped, moniliform. 
pre’cius (Lat.), preco’cious = PRAECOX. 
predom'inant, ‘‘very conspicuous” 
(Braithwaite) ; in excess (Leighton), 
Preflora’‘tion=PRAEFLORATION ; Pre- 
folia’tion = PRAEFOLIATION. 
Preforma'tion (pre, before, formatio, 
a shaping), the theory of the func- 
tion of germ-plasm, 4 complex 
substance whose ultimate factors 
direct the vital activities of the 
cell, and resultant form of the 
plant. 
Prehaustor’ium (pre, before, + Havs- 
TORIUM), papillate epidermal cells 
of Cuscuta, by which nutriment is 
obtained before the formation of 
haustoria (Peirce). 
premorse’ (Crozier) = PRAEMORSUS. 
Prepo’tency (pre, before, sotentia, 
power), the quality by which cer- 
tain pollen fertilizes a given pistil, 
in preference to other pollen. 
Pres’sure, stress or distributed force 
causing turgor or compression ; 
root~, pressure existing in the 
root-tissues tending to cause the 
rise of liquid in the stem. 
preventit‘ious (prae, before, venio, I 
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