342 
AMERICAN JOURNAL OF BOTANY 
[Vol. io, 
initiated at an early stage of germination, or even in the fully mature 
embryo prior to actual germination. 
The plumule is protruded from the cotylar sheath at germination in 
such a way as to lie upon the water surface, the attached seed and ensheath- 
ing embryo adhering to the base of the plumule for some time, the cotyledon 
acting haustorially in the testa. 
Flowers are produced freely in this species in the habitat examined, 
and the presence of minute insects suggests the possibility of insect- 
pollination. 
Flower-formation may be begun by plants with only two or three leaves 
from the seedling, when developed in laboratory dishes. 
State Normal School, 
Danbury, Conn. 
EXPLANATION OF PLATE XXVIII 
Drawings made by aid of an Edinger apparatus; figures 1-6 uniform in magnification 
with the scale shown; figure 7 on smaller scale, as shown. 
Fig. 1. Longitudinal section of carpel and ovule; embryo shaded. Tip region of 
integument tissues changing into “operculum” about micropyle. Axillary bud behind 
carpel at B. 
Figs. 2, 2 a. Longitudinal and cross sections of young embryo, showing early stage 
of development of plumule (stem apex), and inception of sheath about base of plumule. 
Operculum of two forms of cells, short from the inner integument, elongated from the 
outer layer. 
Fig. 3. Embryo in longitudinal section, showing plumule half enclosed by sheath, 
hypocotyl attached to embryo sac without change in character of cells. Cotyledon terminal. 
Fig. 4. Plumule nearly covered by sheath, rudiment of daughter frond present in 
pouch at base of plumule. H, hypocotyl; S, tip of sheath; P, tip of plumule; L 2 , daughter 
frond. 
Fig. 5. Section at right angles to last, but at a little earlier stage, showing the plumule 
as a flattened lobe in upper half of embryo. Age of embryo just prior to that of embryo 
shown in figure 3. 
Fig. 6. Cross section of nearly mature seed with parts identified by key sketch (at 
left). En, endosperm; H, hypocotyl; CS, cotylar sheath; PI, plumule; L 2 , daughter frond. 
Fig. 7. Sagittal section of germinating seed, cotylar sheath with enclosed plumule 
protruded from seed coats, cotyledon retained in testa as “foot.” Endosperm diagram¬ 
matic, water surface indicated by horizontal line, plumule tissue (fine-celled and deeply 
staining) in outline. 
