Seedling Structure of Gy mno sperms, II, 225 
7. Traces of a mesarch structure have been seen in the cotyledonary 
bundles of occasional plants of Tsuga canadensis , Pinus Pinea, and 
P. Gerardiana. 
8. Transfusion tracheides are generally presen t, although the amount 
varies : they have not been observed in Abies pectinata and Cedrus. 
9. Fibrous elements on the dorsal side of the phloem are generally 
present. 
Transition-phenomena. 
10. In the following plants the vascular arrangement takes place within 
the hypocotyl, so that the bundles within the cotyledons are endarch and 
collateral : — Tsuga canadensis, T. diver sifolia, Abies sibirica, A . Veitchii , 
A. balsamea , A.firma , A, Sachaliensis , A, pectinata, A, amabilis , A. magni - 
fica, var. Shastensis, Pice a ajanensis, P. nigra, P. morinda, Cedrus atlantica 
C. Deodar a, Larix occidentals , L. leptolepis, L. europaea, Pseudolarix 
Kaempferi, Pinus Pinea, P. T lumber gii, P, Gerardiana, P. halepensis , 
Araucaria Cunninghams , and A, brasiliensis. 
In the following plants the bundles of some or all of the seed-leaves 
may bifurcate and rotate, more or less markedly, in the cotyledon itself : — 
Pinus Coidteri, P. canariensis , P. australis, P, insignis, P. contorta, P, con - 
torta, var. Murrayana, P. montana, var. gallica , and P, sylvestris, 
11. The cotyledonary bundles behave differently in the vascular 
changes in the transition-region ; and according to their behaviour the 
seed-leaves may represent whole-cotyledons, half-cotyledons, or subsidiary 
cotyledons (see above, Conclusions). 
12. When all the seed-leaves are whole-cotyledons, the transition 
follows Van Tieghem’s Type 3. 
13. Much variation in the transition occurs when the seed-leaves are 
mixed, i. e. when various combinations between the three kinds of cotyle- 
dons occur in the same species. 
14. The polycotyledonous condition has been derived from the 
dicotyledonous condition, in the vast majority of cases by the splitting 
of the seed-leaves and by the promotion of cotyledons from a lower to 
a higher rank. In a few cases, the number of seed-leaves has been 
increased by the displacement of foliage leaves from the first plumular 
whorl to the cotyledonary node. 
15. The relations between the number and nature of the cotyledons 
and the root-structure is shown in the following table. 
