172 REV. PROF. G. HENSLOW ON THE 
differentiated into anti-petaline placental cords and the smaller 
into anti-sepaline dorsal ones. Hence the axis has no longer 
any part in the structure of the pistil. 
The five large placental groups of trachex assume at first a tri- 
lobed form (14) ; then the shape of U’s or V’s, the central lobe (m) 
forming a separate cord situated in the angle. The result is that 
the two rows of ovules belonging to each carpel ultimately face 
the mid-rib of the carpels (19); the margins have, so to say, met 
in the middle and then turned outwards again—not unlike what 
takes place in Cucurbitacee, but to a less extent. The conduct- 
ing-tissue between the rows of ovules which faces the remnant of 
the septa is therefore, as also the whole of the central mass of 
parenchyma, simply the hypertrophied margins which are all 
fused together in forming the column. 
As the distribution of the cords is somewhat complicated, it 
may be advisable to explain the details a little more fully. The 
reader must first carefully compare figs. 14, 15, and 16, and 
observe how the central lobe marked m (14, m) becomes isolated 
in (15) and (16, septal or m), then passes finally to the cir- 
cumferenee, as a septal or marginal cord (7 19). Tt will be 
seen that the 5 dorsal cords (13, 15, 16, 17, d.c.) alternate with 
them. 
The most important point, however, to observe is that one 
branch of each of the two adjacent “U’s” meets the other and 
forms a single line. Thus the two branches under d.c. in figs. 15 
and 16 coalesce and form the uppermost arm of the pentagon 
(17), and finally the ray of cords (19) leading to the ovules, 
Fig. 18 shows the ovular chambers with the septa still existing. 
In fig. 19 the septa have broken away, the ovules are now present 
and face the dorsal cords. 
M. Ph. van Tieghem thought that after the tracheæ had 
coalesced to form the median rays (leading up to the ovuli- 
ferous placentas), an axial cylinder still remained in the middle. 
“En méme temps, les angles rentrants du systéme devenus 
libres reconstituent dans le parenchyme central, un circle 
de dix, faisceaux environ, régulièrement orientes et auquel nous 
devons par conséquent reconnaitre le caractère d'un axe” * 
I must confess that I never could discover anything of the sort. 
The tracheæ are remarkably small, and after the adjacent arms 
* Op. cit. p. 56, 
