28 
The Irish Naturalist. 
February, 
"of black slate in the south-western part of the present sheet were 
"separated out and distinguished as 'Coal-measures,' but, as will be 
''shown in the context, there is now strong reason to doubt whether 
" these beds should be regarded as Coal-measures." 
In the chapter on the superficial deposits an interesting account is 
given of the discovery of " an ancient shore line of earlier date than the 
glaciation of the district." 
Part II. is occupied with a detailed description of the superficial de- 
posits, and comprises 59 pages of closely printed matter of very great 
value. 
Part' III. gives in 18 pages an account of the " Economic Geology" of 
the area under the heads of Building Stone, Slates, Bricks, Silica Clay, 
Sand and Gravel, Road Materials, Water Supply, and Agricultural 
Geology. The latter includes useful notes on soils and subsoils, with a 
table showing their localities, nature, depths, and the petrological 
character of their contents. 
There is a good index and an appendix containing a list of papers on 
the geology of the Cork district. The memoir is illustrated by several 
instructive figures in the text, and by six beautiful photographic plates 
by R. Welch. 
T. F. 
ALIENS, DESIRABLE AND UNDESIRABLE. 
Alien Flora of Britain. By Stephen Troyte Dunn, B.A., F.L.S. 
Pp. 16 + 208. London : West, Newman, and Co. 1905. Price, 5^. 
Before leaving England for Hong Kong in 1903, Mr. Dunn issued a 
" Preliminary List of the Alien Flora of Britain " This was a list only. 
Now, owing chiefly (so he tells us) to the industry of his wife, he has 
been enabled to publish an interesting little book on the same subject, 
in which each of nearly a thousand species has appended to its name a 
note varying in length from a few lines to half a page. These notes 
give the original home of each plant, and state or suggest its mode of 
origin in these islands, but they are a little disappointing in usually not 
giving any indication of the British localities. Trigonella arabica^ 
Delile. — An Oriental weed, once recorded in England among grain 
aliens," does not, after all, convey much more information than was 
given by the inclusion of the bare name in the " Preliminary List." 
But this does not much detract from the value of the book as a record 
of alien immigration and casual introduction. 
Quite the most interesting feature of Mr. Dunn's book is the intro- 
duction, in which the questions of true nativity, of degrees of naturaliza- 
tion, of sources of introduction, and of the evidence to be emploj^ed in 
fixing the standard of plants, are excellently dealt with. We would 
like to see this essay read and taken to heart by every field botanist. 
R. Li., p. 
