1912] STARR— ANATOMY OF DUNE PLANTS 275 



fibers giving general "woodiness" (Euphorbia polygonifolia, Arte- 

 misia, Cirsium, Lithospermum, Prunus, Salix syrticola, Hudsonia, 

 Arctostaphylos, Finns, Hypericum, Juniperus communis, J. 

 virginiana, Quercus), as sclerenchyma (Artemisia, Lathy r us, Am- 

 mophila, Solidago, Prunus pumila, Salix syrticola, Hudsonia, 

 Quercus, Juniperus virginiana), as collenchyma (Artemisia, Cirsium, 

 Solidago, Lithospermum, Salix syrticola, Pinus, Corispermum) ; 

 outer wall of epidermis thick (Cakile, Euphorbia, Lathyrus, Ammo- 

 phila, Lithospermum); cork thick (Artemisia, Prunus, Hypericum, 

 Juniperus communis, J. virginiana). 



Anatomy of root.— Sclerenchymatous generally (Cakile, Cori- 

 spermum, Lathyrus, Solidago); collenchyma in cortex (Solidago); 

 crystals abundant (Solidago, Arenaria, Prunus); resin (Juniperus 

 communis, J. virginiana, Pinus) ; latex (Euphorbia) ; perhaps none 

 but the last is related to xerophytic conditions. 



Slowness of growth is shown by the large number of growth 

 rings in stems of small size (Arctostaphylos, Hypericum, Juniperus 

 communis, J. virginiana), testifying to adverse conditions. Suc- 

 culency usually excludes some other factors, as hairiness and good 

 development of conductive elements. 



Fitting (ii) has recently shown that desert plants apparently 

 do not need longer roots to reach an abundant water supply, as 

 they have a most effective means of obtaining it from a very 

 scanty supply in the high osmotic pressure of their cell sap. Dune 

 plants have not been examined in this respect. It may be found 

 that they too have this " adaptation" to xerophytic conditions. 



II. Comparison of plants growing on the dunes with the 



SAME SPECIES GROWING IN MESOPHYTIC SITUATIONS 



The purpose of this part of the investigation was to find out 

 by careful measurements just how much variation there is in species 

 found in two widely differing habitats. The measurements of 

 sections were made with a micrometer divided into 100 spaces. 

 For the measurement of the leaf, sections were made near the 

 middle, cutting straight across the midrib; an average was taken 

 of several measurements of one leaf and then of several leaves. For 



