760 TRANSACTIONS OF SECTION K. 



Cupressus pisifera, C, Lawso7iiana, and Thuja orientalis all have two coty- 

 ledons, each with a single collateral vascular bundle. The transition phenomena 

 are of the same type as in Taxus, and result iu the formation of a diarch root. 



Libocedrus decuiTens, also, is similar, but the number of seed-leaves is three, 

 and the primary root is triarch. 



Cedrus Deodara. — There are usually eleven or twelve cotyledons; the number, 

 however, varies. Each contains a single collateral endarch bundle throughout its 

 whole length. 



Above the cotyledonary node the seed-leaves fuse to form a well-defined tube, 

 the inner surface of which is corrugated ; each ridge corresponds to a cotyledon, 

 the foliage leaves of the first node fit into the furrows, and, before the axis is 

 reached, these leaves fuse with the cotyledonary tube. Fusion with the axis 

 takes place, and the general appearance of a transverse section, taken immediately 

 below the cotyledonary node, is that of a monocotyledonous stem. This appear- 

 ance is, of course, due to the disposition of the leaf-traces of the first three or four 

 nodes ; these bundles, however, speedily lose their identity, and, a little later, so 

 also do the vascular strands of the first node. The bundles of the cotyledons now 

 become placed closely together, so that the limits of any one is difficult to deter- 

 mine. At a lower level a gradual change occurs; the phloem groups fuse together 

 in pairs, and at the same time the masses of xylem undergo rotation in such a 

 manner that two neighbouring protoxylems become exarch, fuse, and occupy 

 positions alternating with those taken up by the phloem groups. Thus a typical 

 root is formed, usually pentarch or tetrarch. 



Finns Murrayana ■<}?i\\ Sargenti. — Four cotyledons are usually present : each 

 contains a single bundle which has transfusion tracheides adjoining. 



Near the base of the cotyledons the phloem of the bundles bifurcates, and the 

 xylem rotates in such a manner that the protoxylem becomes situated between 

 the two groups of phloem elements. In this condition they enter the axis, and 

 in their passage towards the centre the rearrangement becomes more marked. 

 During the downward course the eight phloem groups fuse in pairs, the meta- 

 xylem takes up a position internal to the phloem, and, as the protoxylem is already 

 exarch, a tetrarch root is formed. 



There is, however, some variation. Thus another seedling also had four coty- 

 ledons, the bundles of three of which exhibited the rearrangement described above 

 while still in the leaf, while the fourth remained undivided throughout its whole 

 course. The central region of the axis being reached, the fourth cotyledonary 

 bundle played the part of a plumular trace, and fused up with the two epicoty- 

 ledonary bundles situated upon its flanks. The other three seed-leaf strands 

 behaved in the manner already indicated above. Their phloem groups joined with 

 the adjacent bast of the plumular bundles, and the same applies to their meta- 

 xylem elements. A triarch root was thus formed. 



Pinus montana var. gallica, P. sylvestris, P. Thmibergii, P. Gerardiana, and 

 others all follow a course similar to the above. There is, however, much varia- 

 tion both in the number of the seed-leaves and also in the behaviour of the bundles 

 of the cotyledons. 



I'suga divevsifolia may be placed in a position intermediate between the Taxia 

 and Pinus types. 



2. On the Seedling Structure of certain Centrospermce. By T. G. Hill. 



NrCTAGlNACEiE : 



Allionia albida, Walt. — The petiole of each cotyledon contains a central strand, 

 consisting only of a very few tracheae, derived from one of the bundles of the midrib, 

 and bounded on each side by two normal collateral bundles, the smaller ones being 

 outermost. Near the base of the petiole the traces a fuse with the larger bundles b. 

 The axis, at the level of the cotyledonary node, contains six plumular strands, 

 which soon fuse together to form two. On the arrival of the seed-leaf bundles 

 into the central cylinder, the groups of tracheae c 1 and c 2 occupy their isolated 



