1906] CURRENT LITERATURE 30i 
with the occurrence of Entomostraca that are also common in pools, leads the 
author to the generalization that the limnetic plankton of the Scottish lakes 
is of littoral origin, and that the transportation of these forms to become a part 
of the limnetic fauna and flora is favored by the steep hillsides surrounding the 
lakes, and the extremely narrow littoral region. 
The author enters upon a somewhat detailed discussion of the influence 
of the organic life upon the lakes themselves, showing how in the Danish lakes 
the algae and higher plants make deposits of lime which are partly thrown upon 
the beach, and partly fall to the bottom in the limnetic region. In these bottom 
deposits it is again worked over by worms and insect larvae, which devour the 
remaining organic matter and leave the bottom sometimes composed almost 
entirely of lime and clay. In the Scottish lakes the bottom in the deeper portions: 
is composed of material largely derived from the littoral and shore regions, and 
there is an absence of lime. 
The general conclusion is that while the Danish lakes are filling up, the 
Scottish lakes will remain with very slight alteration for ages.—C. DwicH 
Mars. 
Chlorosis.—One of the most notable papers recently published on the type 
of diseases which may be classed as chlorosis is that of Baur on the infectious 
chlorosis of the Malvaceae. The variegated mallows in cultivation were derive 
from a form of Abutilon striatum known as A. Thomsoni, which appeared in a 
collection of A. striatum imported into England from the West Indies in 1868. 
This plant was found to be capable of transmitting its variegation by grafting. 
Baur finds that if the leaves are removed from variegated plants, or if the shoots 
are cut back so that no leaves remain and the plants kept in the dark, new shoots 
form only two or three variegated leaves, and if those are removed the plants remain 
permanently green in the light unless they are again infected from scions of varie- 
gated plants. However, if latent axillary buds on the old parts are forced into 
growth, these produce shoots with variegated leaves which in turn infect all newly 
formed leaves on the plant. When all variegated leaves are removed from a 
plant exposed to light, the plant becomes permanently green. Similarly 
Scions of the green but susceptible A. arboreum are grafted on defoliated varie- 
gated plants, the scions remain green, but here also if a variegated shoot is allowed 
‘to develop from the stock it rapidly infects the whole plant. The author concludes 
that the variegation in these plants is caused by a substance or virus which is 
formed only in the light in the chlorotic parts of the plants; that this virus is 
produced only in small excess so that it is rapidly used up if the variegated leaves 
are continually removed. The substance is capable of infecting only the embry- 
onic leaves and in those it is stored for months in an inactive form. By appro- 
priate girdling and grafting experiments the approximate rate of movement and 
the path followed was determined. Movement takes place in the cortex and 
not with the transpiration stream. When scions of immune 4A. arboreum are 
grafted on a variegated A. Thomsoni, they grow vigorously but are not infected; 
