Hill. — On the Seed ling- Structure of certain Piper ales. 163 
two groups, each consisting of three strands, the largest bundles occupying 
a central position in their respective group. Anastomoses take place between 
these plumular traces and the two phloem masses of each cotyledon-bundle, 
the exact junctions being illustrated in the accompanying Diagram I, from 
which it will be seen that, essentially, the lateral bundles, b, c ; e, and /, fuse 
with the nearest cotyledonary phloem mass, and then the four phloem 
groups thus formed take up a more central position, the neighbouring 
phloems joining up to form two groups. The protoxylem is already 
exarch, and occupies its proper position relative .to the bast ; thus a 
typical diarch root obtains (Figs. 4, 5, and 6 , Plate X). 
It has already been pointed out by Tansley and Thomas 1 that this is an 
extreme case of what obtains in other plants. They themselves ‘ have found 
this type in fourteen genera of Ranunculaceae, in certain Berberidaceae, 
and in every genus examined (twenty- four in all) belonging to the orders 
Papaveraceae (including Fumariaceae), Capparidaceae, Resedaceae, and 
Cruciferae \ Sterckx 2 , Gerard 3 , Miss Sargant 4 , and Tansley 5 have 
described the same type as occurring in certain Ranunculaceae and allied 
plants ; Miss Sargant 4 and Chauveaud 6 have drawn attention to the 
presence of a similar type in a number of monocotyledonous plants, and, 
finally, the writer has found it to obtain in certain Centrospermae. Further 
research will show whether the type is of more general occurrence through- 
out the Dicotyledons. 
One of the seedlings examined possessed three cotyledons, the plumule 
was in an embryonic state, and its vascular bundles were much less 
developed than in the plant just described. 
The transition in this tricotyledonary specimen followed precisely 
similar lines to those described for the normal plant. At the cotyledonary 
node each bundle with its bifurcated phloem and exarch protoxylem 
passes inwards, and, as they do so, the phloem groups of each bundle 
separate more and more, until each ultimately comes into contact with a 
phloem group of one of the other cotyledonary traces, so that finally three 
phloems result. The xylem strands converge towards the centre of the 
1 Tansley, A. G. and Thomas, E. N. Root Structure in the Central Cylinder of the Hypocotyl. 
New Phytologist, Vol. iii, No. 4, April, 1904. 
3 Sterckx. Recherches anatomiques sur l’embryon et les plantules dans la famille des Renon- 
culacees. Mem. Soc. Roy. Sci. Liege, s6r. 3, t. ii, 1899. 
3 Gdrard, R. Recherches sur le passage de la Racine k la Tige. Ann. Sci. Nat. Bot. s^r. 6, t. xi, 
1880. 
4 Sargant, E. A Theory of the Origin of Monocotyledons founded on the Structure of their 
Seedlings. Ann. Bot., xvii, 1903. 
5 Tansley, A. G. Reduction in Descent. New Phytologist, Vol. i, 1902. 
6 Chauveaud, M. G. Passage de la position alterne a la position superposee de 1 ’appareil 
conducteur, avec destruction des vaisseaux centripetes primitifs, dans le cotyledon de l’Oignon 
(Allium Cepa). Bull, du Mus. d’Hist. Nat, No. 1, 1902, p. 52. 
Chauveaud, M. G. Sur le passage de la disposition alterne des Elements liberiens et ligneux aleur 
disposition superposee dans le Trocart (Triglochin). Bull, du Mus. d’Hist. Nat., No. 3, 1901, p. 1 24. 
M 2 
