NortH Haven Sanp Pratins 615 
that these last named plants have thick fleshy roots and rhizomes 
that can, doubtless, store water as well as food. These plants 
also have thin-walled cells in the endodermis of the small roots 
opposite the xylem rays, in order to permit the rapid transfer of 
water between the xylem and cortex. 
Linaria Canadensis, which is abundant at North Haven around 
the barren tract, making the field fairly blue in June, has leaves 
that are linear in shape and somewhat succulent. Another class 
of plants, to which belong several members of the Compositae, 
and of which Ambrosia artemisiacfolia, Artemisia caudata and 
Achillea Millefolium may be mentioned, possess finely divided 
leaves which are more or less hairy as a means of reducing the 
loss of water. 
lonactis linariifolius and Chrysopsis falcata have narrow rigid 
leaves exposing a minimum amount of surface and seem well fitted 
for dry situations. A microscopical examination of the leaves 
exhibits special adaptations for conserving the moisture which they 
contain. Both have a much thickened cuticle and in the former 
the stomata are well protected, while the leaf of the latter has a 
palisade layer beneath the epidermis of each surface. 
Sarothra gentianoides (Hypericum nudicaule) has the leaves re- 
duced to mere scaly bracts and the stem contains special water- 
holding cells with thick walls peculiarly pitted and green assimilat- 
ing cells that enable it to perform the function of leaves. The 
Toot system contains large vessels and is well developed for the 
rapid supplying of water. 
The frost flower, Helianthemum majus, a common plant of the 
sand plains, has stem and leaves well protected from excessive loss 
of water by a dense covering of appressed radiating hairs (see pl. 
26,h). The mullein, Verbascum Thapsus, has both surfaces of the 
leaf covered by long branching multicellular hairs, which must be 
a great protection from the loss of water. Similar hairs are found 
On the leaves of Plantanus occidentalis, and are figured by Solere- 
der.*  Antennaria neglecta and Guaphalium obtusifolium (G. poly- 
<ephalum) have a woolly covering of white hairs on the under 
Side of the leaves where the stomata are situated. 
It is in the histology of the grasses and sedges, however, that 
* Solereder, H. Systematische Anatomie der Dicotyledonen, 877, f. 784. 1899. 
