i6. 
hish Societies. 
55 
only diseased tissue. The preparation demonstrated the toothed non- 
chelate mandibles of the genus, adapted for cutting through cell walls. 
D. McArdle demonstrated further details of an interesting character 
in Blasia pusilla, previously shown. A portion of the thallus separated 
from the nerve, showed the first formation of two dorsal rows of leaves 
and the rudimentary stipules or ventral row usually found in the foliose 
group ; the plant, therefore, is one of those forming the connecting link 
between the foliose and frondose sections of Hepaticse. The specimens 
were gathered by Mr. Gunn last year on a wet bank by the roadside, at 
Clifden, Co. Galway. It is evenly distributed in Great Britain, nowhere 
common ; it is also found on the Continent, and the range extends to 
N. Asia and N. America. The male plant is smaller than the female, 
and it may be known at once when not in fruit by the flask -shaped 
receptacles containing gemmae. A remarkable feature in the plant was 
also exhibited, a portion of the thallus showing colonies of Nostoc, which 
evidently settles on a cell in a very young tube stage and develops, finding 
a constant supply of moisture from the thallus which at the outside is 
quite membranous (one cell thick). Immersion in water for some days 
improved the growth of the Nostoc, which occupied a circle in the tissue, and 
from pressure of its growth a ring of cells surrounds it. At this stage the 
colony is easily pushed off the thallus, leaving a circular space with empty 
cells, with the walls thickened and the contents used up; the two outer cells 
of the circle have their walls more thickened than the others, and form a 
shallow rim. When immersed the Nostoc colony grows more conical and 
does not spread beyond the circle formed of thickened cells, and a question 
strikes one — is this an instance of symbiosis of Nostoc with Blasia ? 
No difference in the cells of the thallus, excepting the thickened walls, is 
observable, and probably the host derives no benefit from the Nostoc ; on 
the other hand, the plant, which grows in wet places, serves as a reservoir 
of moisture for the Nostoc in the young state, and probably when mature 
falls off the thallus and completes its life history on marshy earth or wet 
moss. It is remarkable that on the circle of tissue adjacent to where 
a colony has been, the walls are uninjured and unbroken, and that the 
Nostoc does not ramify in the membranous tissue of the liverwort ; and 
there is no apparent difference of growth in the thallus, nearly the whole 
surface of which is occupied. Under a high power a colony was exhibited ; 
it was very like Nostoc muscorum found on mosses in damp places. 
ROYAL ZOOLOGICAL SOCIETY. 
Recent gifts include a Blackbird from Mr. Gore, Finches and Wood- 
pigeons from Mr. R, W. Despard, Doves from Mrs. Phipps and Sir 
Frederick Shaw, and a Swan from the Countess of Kilmorey. 
