CHAPTER IV 
LIFE HISTORY OF AN ANGIOSPERM (ERYTHRONIUM 
AMERICANUM) 
This attractive little plant, commonly called the Dog’s Tooth 
Violet but related to the Lily, is found in the hollows of woods and 
may be seen in flower during the month of April in the Middle 
Atlantic States. It consists of an underground stem bearing scales 
(modified leaves) which is termed a bulb. From the lower surface 
of the bulb are given off numerous slender rootlets which penetrate 
the soil and from the upper surface, a pair of oblong lance-shaped 
leaves of pale green color mottled with purple and white and later, a 
flower stalk {scape) which bears upon its summit a single yellow 
nodding flower which is often marked with purple stripes. The 
flower consists of a torus or receptacle which will be observed as the 
upper swollen end of the flower stalk (scape). Inserted upon it, 
passing from periphery toward the center, will be noted four whorls 
of floral leaves which in order are calyx, corolla, andrcecium and gynce- 
cium. The calyx is composed of three lance-shaped and recurved 
yellow parts called sepals; the corolla of three similarly looking 
parts called petals which alternate in position with the sepals. 
Both of these whorls are collectively called the perianth or floral 
envelope. The androecium or male system of organs is composed 
of two whorls or circles of structures called microsporophylls or 
stamens. There are three stamens in each whorl. The outer whorl 
of stamens will be found opposite the sepals while the inner will be 
observed opposite the petals. Each stamen (microsporophyll) con- 
sists of an awl-shaped stalk or filament bearing upon its summit an 
oblong-linear body called an anther. The anther consists of two 
lobes called microsori. Each lobe or microsorus contains two anther 
sacs or microsporangia in which when mature are to be found micro- 
spores or pollen grains. In the center of the flower will be noted 
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