30 BOTANICAL GAZETTE [JANUARY 
Tuomas, ETHEL N., A theory of the —— leaf trace founded on seedling 
structure. New Phytol. 6: 77-01. ; 
WetTsTEIN, R. R. v., Handbuch det Spacematiochen Botanik. Vol. IL. 
WIELAND, G. R., American fossil cycads. Washington. 1906. 
WorsbDELL, W. C., A study of the vascular system in certain orders of 
the Hasdles. Ann. Botany 22: 651-682. 1908. 
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wo N H 
EXPLANATION OF PLATES I-III 
All drawings were made with the aid of a camera lucida from microtome 
sections. 
Abbreviations used: a, antipodal; ar, pga aay cb, cortical bundle; 
cc, central cylinder; c, cotyledon; e, egg; em, embryo; es, endosperm; vb, 
fibrovascular bundle; iz, inner integument; -. mechanical tissue; mgmc, 
megaspore mother cell; mg, megaspore; mcmc, microspore mother cell; 
mp, micropyle; m, nucellus; oi, outer integument; 7, pith; pc, parietal cells; 
ph, phloem; pu, polar nucleus; #/, pollen tube; st, sporogenous tissue; su, 
suspensor; sy, synergid; #, tapetum; fc, tapetal cell; fe, tetrad; v, vacuole; 
x, xylem. 
Liriodendron 
Fic. 1.—Part of longitudinal section of microsporangium and wall; 
wall somewhat diagrammatic; 350. 
IG. 2.—Pollen mother cells dividing; 350 
Fic. 3.—Section of pollef grain with reduced number of chromosomes; 
X 600. 
Fic. 4.—Section of two-celled pollen grain; 350. 
°. 
Fic. 7.—Longitudinal section . ovary showing tetrad of megaspores 
— buried within nucellus; 35 
8.—Longitudinal section is tnictopylat end of embryo sac; 350. 
Fic. 9.—Polar nuclei fusing; X 350. 
Fic. 10.—Longitudinal section of antipodal end of embryo sac; 350. 
Fic. 11.—Transverse section of petiole showing arrangement of fibro- 
vascular bundles; X 50. 
Fic. 12.—Transverse section of portion of central region of diarch root; 
go. 
ee 13.—Transverse section of hypocotyl; X 50. 
G. 14.—Transverse section showing details of the portion of fig. 13 
tae by line ab; X 300. 
Magnolia 
Fic. 15.—Longitudinal section of part of anther; sporogenous tissue 
differentiated; 350. 
