panying plates: the first (Pl. X.) with large hairy buds and rather large fruit with coarse cup-scales, the second (Pl. XI.) with mediumsized nearly smooth buds and moderate or large fruit with rather closer or finer scales, and the third (Pl. XII.) with still smaller buds and acorns, these with still closer and finer cupule-scales. That the groups are closely allied is to be expected, and in bud and cup characters Q. coccinea connects the first two; but a glance at the plates will show how distinct the collective impression produced by each group is, and how far from natural it is to place Q. marilandica (Pl. X., f. 1) next Q. nigra (Pl. XII., f. 2) because of a comparability in leaf shape that has worked mischief in the names both have borne, or Q. palustris (Pl. XII., f. 1) next Q. rubra (Pl. XI., f. 5) or Q. velutina (Pl. X., f. 4), or to separate Q. Catesbæi (Pl. X., f. 2) far from Q. digitata (Pl. X., f. 3) or even Q. marilandica, as is commonly done. An interesting feature in the cup of these latter species is that the scales are inflexed around its margin-commonly in the first, occasionally in the others—a character to be connected with Engelmann's observation11 that the tips of the leaf lobes are bent in in vernation in Catesbæi, though it is not absolutely limited to them.

Though homogeneous in external bud and fruit characters, the group of swamp oaks is subdivisible into a series with broad-lobed leaves, the water oaks, in which the leaves are flatly imbricated in the bud as in the black and scarlet oaks, and a series with narrow entire leaves, the willow oaks, in which the leaves are revolute in the bud-strongly so in Q. imbricaria, Q. Phellos, Q. laurifolia and Q. pumila; less rolled in Q. cinerea and Q. myrtifolia, and thus approaching the western groups, though the fruits of the two are very different. Such Mexican bristle-leaved oaks as Q. Grabami are evidently of this general stock.

Grouped primarily according to the characters here selected rather than leaf form, these oaks fall into line as follows:

Quercus digitata (Spanish oak).
Quercus velutina (quercitron).

SCARLET OAKS.

Quercus coccinea (scarlet oak).
Quercus ellipsoidalis (Hill's oak).
Quercus rubra (red oak).

Quercus texana (Texas red oak).

Quercus nana (bear oak).

SWAMP OAKS.

Water oaks.

Quercus palustris (pin oak).

Quercus nigra (water oak).

Quercus georgiana (Stone Mountain oak).

Willow oaks.

Quercus imbricaria (shingle oak).

Quercus Phellos (willow oak).

Quercus laurifolia (laurel oak).

Quercus pumila (running oak).

Quercus brevifolia (cinnamon oak).
Quercus myrtifolia (myrtle oak).

OLIVE OAKS.

Quercus hypoleuca (white-leaf oak).
Quercus Emoryi (Emory's oak).
HOLLY OAKS.

Quercus agrifolia (evergreen oak).
Quercus Wislizeni (highland oak).
Quercus californica (Kellogg's oak).

EXPLANATION OF PLATES.

In all, the buds are enlarged three diameters, and the acorns and cupules are of natural size. No special care has been taken in the selection of material, except to get mature winter buds because the differences are less evident while they are developing, and to pick out average fruits from the varying assemblage presented by each species.

PLATE X. BLACK OAKS.—I, Quercus marilandica; 2, Q. Catesbæi; 3, Q. digitata; 4, Q. velutina.

PLATE XI. SCARLET OAKS.-1, Quercus coccinea; 2, Q. ellipsoidalis; 3, Q. texana (the northern form known also as Q. Schneckii); 4, Q. texana (from Texas); 5, Q. rubra; 6, Q. nana.

PLATE XII. SWAMP OAKS.-Water Oaks: 1, Quercus palustris; 2, Q. nigra; 3, Q. georgiana. Willow Oaks: 4, Quercus imbricaria; 5, Q. Phellos; 6. Q. laurifolia; 7, Q. pumila; 8, Q. brevifolia; 9, Q. myrtifolia.

PLATE XIII. WESTERN BLACK OAKS.-Olive Oaks: 1, Quercus hypoleuca; 2, Q. Emoryi. Holly Oaks: 3, Quercus agrifolia; 4, Q. Wislizeni; 5, Q. californica.