1912] CURRENT LITERATURE 87 
yeast apparently has a surface tension of about 0.60. The article seems to 
clear away much of the haze that has surrounded the matter of the significance 
of surface tension in cell activity—WILLIAM CROCKER. 
Underground organs of weeds.—Conflicting statements by various authors 
have induced PamMet and FoGEL?} to investigate the organs of vegetative 
reproduction of some of our most common weeds. The Canada thistle (Cir- 
sium arvense), the horse nettle (Solanum carolinense), the milkweed (Asclepias 
syriaca), and the bindweed (Convolvulus arvensis), were all found to be propa- 
gated by horizontal roots bearing adventitious buds; while in the wild morning 
glory (Convolvulus Sepium) and the quack grass (Agropyron repens), the organs 
of vegetative multiplication are rootstocks. In some instances the roots and 
subterranean stems resembled each other so closely that only by microscopic 
examination could the difference be detected.—Gro. D. FULLER 
Epidermis and light refraction.—F Rimmel” thinks he has shown that the 
lower papillate epidermis of the leaves of the yew gives a total refraction of 
the light passing through the leaf from above, thereby leading to the use of 
all light that enters the leaf. He relates this character to the ability of the 
tree to grow in shaded habitats. He believes the lower epidermis of a number 
of other conifers acts in the same way. He finds a similar contrivance in the 
spongy parenchyma of the cotyledon of the beech. The fact of total refraction 
in the yew seems entirely established; whether it is of biological significance 
or not is quite another question.—WILLIAM CROCKER. 
Arctic vegetation.—Hare Island off the coast of West Greenland, an 
uninhabited island 66 square miles in area, has been visited several times by 
PorsILp,”> who has found a flora consisting of 82 arctic and 30 subarctic species. 
The vegetation belongs to the fell-field formation, large areas quite devoid 
of plants, passing into a poorly developed heath with arctic meadows and bogs 
in the more sheltered situations. Dispersal is almost entirely through the 
agency of the wind over the surface of the snow and frozen seas. The sub- 
arctic species are regarded as relics of milder climate in post-glacial times.— 
EO. D. FULLER 
Pneumatophores.—From an examination of the tissues of vertical apogeo- 
tropic branches of the roots of Terminalia Arjuna, a large tree of Central India, 
73 PAMMEL, L. H., and FocEL, EsTELLE eb The underground organs of a few 
weeds. Proc. Iowa Acad. Sci. 16:pp. 7. pls. 5 
74 FRIMMEL, FRANZ v., Die untere ola des Taxus-Blattes ein Lichtreflektor, ° 
Oester. Bot. Zeitsch. sr: 216-223. figs. 
5 Porsttp, Mortem P., The plant oe of a. Island off the coast of West Green- 
land. Sactiryk af ‘Meddelelser om Gronland 47:252-274. figs. 10. Kobenhavn 
Bianco Lunos. 1910. 
