PHYLLACTIDIUM. 225 
both upper and under surface. On dissection they present two vascu- 
lar bundles, one on either side of the middle line, in which respect 
they differ essentially from those scales which, in young specimens of 
this plant, are occasionally developed as elongated green leaves, and 
Which invariably exhibit a mesial vascular bundle or midrib. e 
axillary bodies performing leaf functions in Sciadopitys, therefore, 
are distinguished from true leaves, not only by their position but by 
their structure, and I think that most botanists will agree with me in 
referring them to the category of phylloid shoots analogous to those in 
Phyliocladus, ete. 
PHYLLACTIDIUM, A GENUS OF FRESHWATER ALGA 
NEW TO THE ENGLISH FLORA. 
By Dr. Jons Epwarp Gray, F.R.S., ETC. 
Mr. Aylward, of Strangeway, Manchester, has kindly sent me a 
minute plant, which he discovered while searching for water insects in 
a small round shallow pond, near the back of the New Assize Court, 
at Manchester. He observes, “ The plant gradually developed itself in 
the water when placed in a bottle. The plant adheres to the side of 
the bottle, and forms a flattish cone, and round the edge of its base 
throws out delicate white rootlets, which swim freely in the water, 
and might be mistaken for confervoid growth.” 
The plant is evidently Phyllactidium pulchellum of Kützing's Phyc. 
Gener, 297 L 16 f 1L The form is diseoidal, circular, slightly 
concave on one side, formed of very many very minute, nearly equal- 
sized, square cells, placed on forked lines regularly spreading from a 
central cell to the circumference ; the frond is thin, membranaceous, 
and the upper and under surfaces are similar. The fructification con- 
sists of 12 to 16 square thickened patches, forming a circle (some- 
times two) rather nearer the margin than the centre of the disk, the 
Kützing places Phyllactidium next to Coleochete, with Conferva. 
See ‘Species Algarum,’ p. 424. Rabenhorst, in his Cryptogamic Flora 
VOL. Iv. [JULY 1, 1866.] Q 
