THE 
NEW PHYTOItOGIST. 
Vol. XV, Nos. 5 & 6. 
May & June, 1916 . 
[Published July 24th, 1916]. 
ON A NEW PENETRATING ALGA. 
By Elizabeth Acton, M.Sc. 
[With Plate I and Two Figures in the Text]. 
HE alga here described appeared in an ordinary white pie-dish 
which had been standing for some years in the laboratory. 
The dish contained “ Cladophora balls ” collected a few years 
previously from Loch Kildona in South Uist. 
Pale green patches suddenly began to form on the sides and 
floor of the dish. These increased gradually in size until the dish 
was nearly covered by them, but they have not increased in 
number since they first appeared. See Plate I. 
It was impossible to remove these patches by rubbing or 
scraping the surface of the dish, so that they were evidently grow¬ 
ing underneath the glaze. In order to examine the alga, it was 
necessary to chip minute fragments of glaze from the surface of 
the dish and mount these on a slide. In this way it was possible to 
ascertain that a small filamentous green alga was growing between 
the glaze and porcelain of the dish, and by its growth, was separat¬ 
ing the one from the other. The concentric zoning of the patches 
shewed that branches were extending radially parallel to the surface, 
but no branches were seen to penetrate either the porcelain or the 
glaze. 
It will be obvious that fragments of a thallus obtained in this 
way were not sufficient for a complete investigation. No other 
dish in the laboratory shewed traces of this alga, and as the dish in 
question had contained only “ Cladophora balls,” these were 
examined to see if they contained a similar alga. 
It was found that many of the dead cells of the Cladophora 
were covered by a small alga . 1 This was compared with the alga 
1 Cladophora (Aegagropila) holsatica (the alga forming the balls) has very 
thick lamellose walls which persist for some time after the death of the cell in 
an apparently unchanged condition. 
