1917] CURRENT LITERATURE 85 
on them. While the author speaks of sterilizing the seeds with bromine, he 
says nothing about making cultures to assure that they are sterile. Many 
authors find it difficult to sterilize seeds without killing them. This is spe- 
cially true of those with open micropyles. From the first two papers of the 
series, Kipp reemphasizes his conception that the dormancy of “moist seeds” 
is due to the anesthetic action of carbon dioxide which is held in by seed coats. 
If this be the cause of dormancy in any imbibed seeds, it is limited in its appli- 
cation. It does not apply to seeds which have a rest period during which the 
embryo is developing; to seeds like Alisma and Amaranthus, in which the 
swelling contents do not have sufficient pressure to break the coats; or to 
seeds like Crataegus, in which the embryos are dormant when naked.” has 
by no means proved that this holds even for forms forced by increased oxygen 
pressure (Xanthiwm and others). His conception implies that the coats of 
ese seeds are very slightly permeable to CO.. In the elementary course in 
plant physiology in Hull Botanical Laboratory, we used for years various seed 
coats and the epidermis of various leaves to show that moist plant membranes: 
are relatively very permeable to CO, in contrast to oxygen and nitrogen. 
Kipp’s assumption concerning CO, and dormancy of seeds, therefore, even 
under limited application, cannot be considered more than an hypothesis. 
without a study of the amunera character of the seed coats to CO, and 
other gases.—W™M. CROCKER 
Vegetation of South Africa.—In a region where climate differs strikingly 
over areas of comparatively small size, there is usually a corresponding diver- 
sity of vegetation. Apparently such diversity is displayed to a r 
in South Africa, as seen in the recent studies by Bews. In his earlier : 
papers, reviewed in this journal, 3 a general account of tl f Natal 
was given and a more detailed study of some areas within its limits. Inhis 
latest article Brews“ has sketched the vegetation of a wider area and has — 
begun the study of its succession. The condition of Table Mountain is per- 
of Go-7é cm. ‘atiniathy and resulting pape tao scrub communities, while 
“upon the eastern slopes the precipitation is doubled and a rather mesophytic 
forest results. The 
and passes from e fell field with open en ol ose , Crassulaceae, Com- ie 
| Pra Ra, Pi aya a een eae many 
_ bulbous tyledons, a -onspicu 
