PLANT STUDIES 
PETAL : one of the floral leaves which make up the corolla. 
PHOTOSYNTHESIS : the process by which chloroplasts, aided by light, 
manufacture carbohydrates from carbon dioxide and water. 
PISTIL : the central organ of the flower, composed of one or more car- 
pels. 
PISTILLATE : applied to flowers with carpels but no stamens. 
POLLEN : the microspores of Spermatophytes. 
POLLEN-TUBE : the tube developed from the wall of the pollen grain 
which penetrates to the egg and conducts the male cells. 
POLLINATION : the transfer of pollen from anther to ovule (in Gymno- 
sperms) or stigma (in Angiosperms). 
POLYPETALOUS : applied to flowers whose petals are free from one an- 
other. 
PROTHALLIUM : the gametophyte of Ferns. 
PROTONEMA : the thallus portion of the gametophyte of Mosses. 
RECEPTACLE : in Angiosperms that part of the stem which is more or 
less modified to support the parts of the flower. 
RHIZOID : a hair-like process developed by the lower plants and by in- 
dependent gametophytes to act as a holdfast or absorbing organ, 
or both. 
SAPROPHYTE : a plant which obtains food from the dead bodies or body 
products of plants or animals. 
SCALE : a leaf without chlorophyll, and usually reduced in size. 
SEPAL : one of the floral leaves which make up the calyx. 
SEXUAL SPORE : one produced by the union of gametes. 
SPERM : the male gamete. 
SPIRAL : applied to an arrangement of leaves or floral parts in which 
no two appear upon the axis at the same level ; often called alter- 
nate. 
SPORANGIUM: the organ within which asexual spores are produced 
(except in Bryophytes). 
SPORE : a cell set apart for reproduction. 
SPOROGONIUM : the leafless sporophyte of Bryophytes. 
SPOROPHORE : a special branch bearing asexual spores. 
SPOROPHYLL : a leaf set apart to produce sporangia. 
SPOROPHYTE : in alternation of generations, the generation which pro- 
duces the asexual spores. 
STAMEN : the microsporophyll of Spermatophytes. 
STAMINATE : applied to a flower with stamens but no carpels. 
STIGMA : in Angiosperms that portion of the carpel (usually of the style) 
prepared to receive pollen. 
