Seedling Anatomy of Certain Sympelalae . II. 319 
tricotyledonary seedlings. Working from root to cotyledons, the diarch 
stele gives place in the hypocotyl to four collateral strands — the two large 
ones in the plane of the diarch plate (corresponding to the plane of the 
cotyledons in an ordinary seedling), and two 
small ones in a plane at right angles to the 
diarch (intercotyledonary plane in an ordinary 
seedling), (Diagram 10 , IV and V). If two of the 
cotyledons really correspond to one in the dico- 
tyledonous seedling, it follows that half the 
vascular tissue should supply one of the three 
cotyledons, while the other half should do duty 
for the remaining two cotyledons ; which is 
what actually happens. One of the large 
bundles (y) and half of each small one (x and z) 
pass to a single cotyledon, while the remaining 
halves of the small strands form one of the lateral 
bundles in each of the other cotyledons. The 
other large strand divides into three — two large 
bundles, each forming a midrib, and a small 
bundle which bifurcates so as to supply the 
two lateral strands required (compare with 
Diagram 10, 1, II, and III). 
Thus the anatomy, also, supports the view that two of the seed-leaves 
are homologous with one in the dicotyledonous seedling. 
Text-fig. i. Dimorphotheca 
pluvialis. A and B represent 
seedlings showing two stages in 
the production of the tricotyle- 
donous condition, a , b , c (from 
actual specimens) show stages in 
division of one cotyledon into two. 
Tribe X. Arctotideae. 
Arctotis calendacea , Linn .(Cryptostema calendulaceum , R. Br.). Although 
the seedlings are much larger than those of Charieis heterophy lla, the transi- 
tion is similar, the lateral strands of the cotyledon, after fusing in the 
hypocotyl, passing to the centre to form the core of the diarch root. The 
transition, which is completed at a high level, begins in the cotyledonary 
tube. 
Tribe XI. Cynareae. 
Arctium majus , Bernh. In this species the seedlings, which are generally 
about 6-8 cm. long, are each provided with two rather fleshy, equal cotyledons, 
which possess a peculiar venation. Near the base of each seed-leaf there 
are the usual three bundles — a large midrib and two small laterals. The 
latter follow the margins of the cotyledon to the apex, where they are joined 
by the midrib and its chief branches, which arise in the following manner. 
In the upper half of the seed-leaf the midrib gives off its branches, which 
run outwards at an acute angle and join the laterals somewhat nearer 
the apex; but before doing so each gives rise to a branch which runs 
