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to consist in the greater age of the plant, which varies greatly in 
structure at different seasons, the reticulations becoming more 
complex as the autumn advances. 
I have not been able to find any other published account of the 
occurrence of Clathrocystis than those mentioned above. 
In June 1870, I discovered a large amount of it in the lake at 
Sandringham. 
The surface of the water was covered with the green scum 
mentioned by Henfrey and on examining more closely I found 
that the plant was dispersed uniformly throughout the body of water. 
The characteristic verdigris-green formed by the dried plant was 
well marked on the stones above the water line. 
In September of the same year, I find the following entry in my 
note book : “ The frustules are surrounded by extremely fine 
moniliform filaments of spirillum.” 
On reading Henfrey’s notice of the discovery of the plant at 
Kew, it occurred to me that possibly it might have been introduced 
thence at some time, or other, with aquatic plants ; but on making 
enquiry of the then head gardener, Mr. Carmichael, he informed 
that no plants had ever been brought from Kew, and indeed at 
that time there were none growing in the lake. 
In October of the present year (1875), when driving past a pond 
at Anmer Hall, two miles distant from Sandringham, my attention 
was attracted by the peculiar scum on the surface, which was at 
once recognized as Clathrocystis (a portion of which I have for- 
warded to the Society). 
It seems very probable that it has been recently introduced here, 
most likely by the agency of wild-fowl for I have been in the habit 
of passing the pond frequently and at all times of the year for the 
last eighteen years and so striking an appearance would, I think 
scarcely have escaped my notice. 
It will be interesting to know if other localities have been, or 
should hereafter be, discovered in this county. — John Lowe, M.D. 
Ambrosia peruviana. — A species of Ambrosia closely resembling 
if not identical with the above, was found this autumn (1875) by the 
Ticv. E. W. Dowell in a clover field at Bolwick Hall, Marsham. 
A. peruviana has been recorded as an alien in Yorkshire and Kent, 
and is supposed to have been imported with clover seed from the 
Argentine Republic. — II. D. Geldart. 
