ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
305 
Annual Rings of Growth in Carboniferous Wood. — W. Goldring 
( Bot . Gaz ., 1921, 72 , 326-30, 1 pi.). An account of the annual rings 
of growth in species of Gordaites of the Carboniferous period. A speci- 
men of G. recentium lately found in Oklahoma Forest (which is practically 
in the same latitude as the Triassic forests) shows distinct annual rings. 
So far as is known this is the most southern occurrence of Carboniferous 
wood with annual rings of growth w 7 hich has been noted. According 
to Jeffrey such rings indicate a marked variation in the annual tempera- 
ture, so that this variation must have existed towards the end of the 
Carboniferous period. The rings are very distinct, and in transverse 
section vary from 3 to 8 mm. in width. On the weathered surface of 
the trunk they are equally distinct, and vary from 3 to 7*5 mm. in 
width. The round bordered pits in a single row on the radial walls of 
the tracheids distinguish G. recentium from G. materiarium. The rays 
are numerous, very long, usually uniseriate, never entirely biseriate, and 
are composed of 2 to 47 cells. G. recentium resembles Dadoxylon 
antiquum in having a single row of bordered pits, but differs from it in 
the practically uniseriate rays. S. G. 
Diameter-growth in Box-Elder and Blue Spruce. — C. F. Korstian 
( j Bot. Gaz., 1921, 71 , 454-61, 1 fig.). An account of experiments 
carried out with MacDougal’s dendrograph for recording the changes 
in the size of tree-trunks due to growth and other causes. The first 
experiment was carried out during April and May with Acer Negundo. 
The first few days were cold and stormy and the tree remained quiescent, 
with alternate contraction and enlargement of its diameter. Slight 
growth then began, but ceased during four windy days. The leaves had 
reached about half their natural size before the main period of growth 
began. When there was little difference between the day and night 
temperature there was little change in diameter, but when the nights 
were cold there was considerable difference in diameter. The second 
experiment was made with Picea Parry ana soon after growth had 
begun. This growth continued for a little over five weeks, except for 
two rest periods of two days each. Here again temperature was an 
important factor, since a marked diminution caused decrease or cessation 
of growth. It was also shown that growth does not begin in deciduous 
hardwood trees at the same period as in evergreen conifers ; in the 
latter it may be simultaneous with the bursting of the buds, while in 
the former it may be delayed until the young leaves are large enough 
to manufacture their own food. The dendograph will probably prove 
of much use to foresters in determining the factors most influential in 
the growth of trees. S. G. 
Growth-rings in Monocotyledons. — C. J. Chamberlain {Bot. 
Gaz., 1921, 72 , 293-304, 16 figs.). An account of the discovery of 
growth-rings in Aloe ferox. This species, which is a true xerophyte, 
was found near Grahamstown in South Africa. Its stem was 3 metres 
high and 15 cm. in diameter. In transverse section the zone of 
secondary xylem was 2 cm. across and the cortex 4 mm. ; the central 
region of primary tissues was nearly 10 cm. across ; and the whole section 
had the appearance of a large pith surrounded by a narrow band of 
