A Jurassic Wood from Scotland. 
205 
Summary. 
In each cell of Zygnema evicetormn there is normally only one 
large axile chloroplast of indefinite outline. It is usually constricted 
in the middle and in some cases twisted. There are two large 
pyrenoids, one in each half of the chloroplast. In very many 
cases the chloroplast is partially or wholly masked by numerous oil- 
globules. 
There is experimental evidence that a low temperature 
causes a thickening of the cell-wall and the production of cysts. 
Filaments of the aquatic form grow well in a 0-2 per cent. 
Knop’s solution. 
Filaments of the terrestrial form when placed in water 
gradually fragment and become dissociated into short lengths of 
cells; which may, however, ultimately grow into long filaments. 
If placed in 0'1 per cent. Knop’s solution similar fragmentation 
occurs, but is longer delayed. 
When allowed to dry gradually, the filaments fragment into 
thick-walled “ cysts.” 
The genus Zygogonium as founded by Kiitzing (1843) is unten¬ 
able, and available evidence does not support the retention of 
Zygogonium on the basis put forward by De Bary (1858) and Wille 
(1909). 
Botanical Laboratory, 
Birmingham University. 
A JURASSIC WOOD FROM SCOTLAND. 
By Ruth Holden. 
[With Plate III]. 
T HE Jurassic strata of north-east Scotland have been known in 
a general way since the time of Hu^h Miller (11), but it is 
only comparatively recently that they have been accurately corre¬ 
lated with those of England and of continental Europe. A concise 
account of their lithological and palaeontological character is given 
by Mr. H. B. Woodward (14), while the plant remains are described 
in detail by Seward (14), Seward and Bancroft (15), and Stopes (17). 
Up to the present, there has been but one structurally preserved 
specimen of petrified wood found in that region, viz., Cedroxylon 
Hornei from the Upper Oolite of Helmsdale (15). Dr. E. A. Newell 
Arber, however, secured a large specimen from the Corallian of 
