130 Seward and Gowan .— The Maidenhair 
tains a prothallus of three to five cells and the exine embraces 
two-thirds of the circumference. The pollen-tube grows 
towards the top of the nucellus, and at the beginning of July 
the distal end of the tube becomes branched and fixes itself 
near the apical nucellar protuberance, the pollen-grain end 
being next the archegonia. The nucleus of the innermost 
prothallus-cell divides, and one daughter-nucleus is pushed 
out from the mother-cell; this cell (‘ body-cell ’ of Strasburger) 
grows in size and reaches its maximum about the middle of 
August. Some days before fertilization the cell divides, and 
finally two large antherozoids are produced h 
III. Shoot and Root 1 2 . 
i. Leaf-traces. 
The course of the leaf-traces in shoots of Ginkgo has been 
described by Thomas 3 , Geyler 4 , and other writers. Close to 
the apex of a shoot 5 the vascular bundles of a foliage-leaf 
make their appearance as double strands, and the leaf-traces 
in the upper part of the shoot have the form of distinct 
bundles which in the lower region constitute a continuous ring. 
Each double leaf-trace passes through four internodes before 
becoming a part of the stele ; the double form of the trace is 
especially characteristic of Ginkgo 6 . The first indication of 
the separation of a leaf-trace from the stele of the shoot, as 
seen in transverse section, is the intrusion of two blunt wedges 
1 Hirase (’94), p. 360 , and (’98) ; Strasburger (’92), PI. I; Belajeff (’97), p. 338 ; 
Webber (’97). 
2 For references to the anatomy of Ginkgo, vide Mohl (’32), p. 411 ; Hartig(’48), 
p. 123 ; Goppert (’50), pp. 54 et seq., Pis. IX and XIII; Dippel (’62) and (’63) ; 
Kraus (’64), pp. 146 , &c., and (’ 86 ), pp. 102 , &c.; Van Tieghem (’70), p. 186 ; 
Bertrand (’74); Hohnel (77), p. 535 ; Moeller (’82), Fig. 21 ; Nakamura (’83), 
p. 25 ; Gardner (’83); Goppert (’83) ; Schulz (’83) ; Saporta (’84), pp. 20 etseq. ; 
Essner (’ 86 ), pp. 10 , &c.; Felix (’94). 
3 Thomas (’65). 
4 Geyler (’67) ; vide also Nageli [quoted by Bertrand (’74)]. 
5 Strasburger (’72), p. 327 ; vide also Fankhauser (’82). 
8 Williamson (’83), PI. XXXIII, Figs. 28 and 29 . 
