886 BOTANICAL SURVEY OF DISMAL SWAMP REGION. 



lower in Cakile), radiate in all directions like the spokes of a wheel. 

 Oeriofiiero humifusa is a particularly characteristic representative of 

 the radiant form, one specimen observed having "1\ branches from 3 

 to i) decimeters (1 to ;J feet) in length. In Lechea it is the sterile, 

 leafy, basal shoots that assume this form. The root in this species is 

 comparatively long (about. 3 decimeters) and vertical. In Meibomia 

 the longest branches sometimes measure decimeters ()5 feet) in 

 length. It is possible that the radiant form, as well as the preced- 

 ing, is also useful to the plant by retarding evaporation from the 

 area of sand thus shaded, consequently insuring a supply of water 

 near the surface of the soil between rains. As the under side of the 

 steins and leaves of plants which have this habit of growth are effec- 

 tually protected against light, and heat radiated from the surface of 

 the sand, and to a large extent from exposure to the air, their rate 

 of transpiration must be proportionately much less than in plants not 

 possessing this habit. 



4. The rosette form. — "Rosette plants," which have most of their 

 leaves at the base of the stem and appressed to the soil, are pro- 

 tected in the same manner as plants of the radiant form. They are 

 rare on the strand of Virginia and North Carolina, but are not uncom- 

 mon on the coast of northern Europe. Two (probably) winter an- 

 nuals, Gw-apJialium purpureum and Linaria canadensis, have their 

 basal leaves arranged in a flat rosette. In the latter species these are 

 borne on short horizontal branches. 



5. The cushion or hassock (" Pointer") form. — This life form, which 

 is so strikingly developed in the high Andes, in Australasia, and else- 

 where, is hardly to be included among those of the Virginia strand, 

 unless one refers here the peculiar mode of growth of Hudsonia 

 tom&ntosa, which has numerous short, erect branches. These are 

 densely clothed with appressed, scale-like leaves, and stand closely 

 together. The roots of the Hudsonia are small (the longest about 15 

 centimeters, (J inches, long), and afford the plant but a weak anchor- 

 age in the soil. Consequently the species grows most abundantly in 

 the sheltered hollows among the dunes. 



V). The sod form. {"Rasenform"). — This is represented by Festuca 

 rubra alone, and does not occur in the dune area proper. 



7. The thicket form. — This life form, closely analogous to the two 

 preceding, characterizes several of the shrubby species, notably 

 Myrica carolinensis. Farther south along the coast Hex vomitoria, 

 Quercus virginiana, and other species form strand thickets. 1 By this 

 mode of growth the individual plants are in large measure pro- 

 tected against, the sun and the wind, and the habit may well be inter- 

 preted as an adaptation against excessive transpiration, as well as 

 against the mechanical force of the wind. The compact, rounded 



1 Kearney, Contr. U. S. Nat. Herb., voL 5, p. 272. 



