founded on the Structure of their Seedlings. 23 
In most Monocotyledons the piliferous layer of the root is 
a direct continuation of the cell-layer lying immediately 
under the epidermis of the cotyledon. The absence of the 
epidermal layer causes an abrupt decrease in diameter at the 
junction of the root with the hypocotyl, and the ‘ collet’ is 
defined by Van Tieghem as a plane passing through the axis 
immediately below the last row of epidermal cells. 
The root of Albuca , however, has a greater diameter than 
the hypocotyl in the region where they join, and the same is 
true of many other species belonging to this tribe. The 
increase in girth is due to repeated tangential division in the 
cells of the outer cortical layer. The external layer of cells in 
the tissue thus formed is of course the piliferous layer. 
Hitherto Erythronium is the only genus outside the Scilleae 
in which I have found this development of the cortex. I do 
not propose to do more than mention its existence here, but 
hope shortly to describe it in greater detail elsewhere. 
2. Tribe Tulipeae. 
The variety of vascular structure characteristic of seed- 
lings belonging to the Scilleae is in strong contrast with 
the uniformity of type found in the Tulipeae. I have fully 
examined eight species belonging to four genera of this tribe, 
and with the exception of Erythronium the vascular sym- 
metry of the cotyledon and the process of transition from 
stem to root are the same in all. 
Fritillaria imperialis. The seedling of this species (PI. Ill, 
Fig. 1) consists of cotyledon, hypocotyl, and primary root 
throughout the first season. The petiole of the cotyledon 
becomes flattened and acts as an assimilating organ. Neither 
foliage leaf nor cauline root is developed until the second 
season of growth. The primary root is very well developed. 
The massive bundles run the whole length of the cotyledon. 
They lie close together in the sheath, but are quite distinct 
(PI. Ill, Fig. 2). The plumule is still embryonic : its bun- 
dles become lignified lower down, where they unite to form 
