DUBLIN MICROSCOPICAL CLUB. 
115 
23rc? OctoheTi 1879. 
Peculiarity in Histological Structure of Spine of JEchinothrioe 
Turcarum, Peters. — Prof. H. W. Mackintosh exhibited a cross sec- 
tion of the spine of HcTiinothrix Turcarum, Peters, and called atten- 
tion to a peculiarity in its structure, of which this was, so far, the 
only example he had met. In the normal spine the solid wedges 
are coextensive with the network between them, but in this form 
they were produced beyond it, reminding one somewhat of the 
arrangement in the spine of Echinus lividus. The specimen from 
which the spire had been taken formed part of a collection made 
by Professor E. P. Wright in the Seychelles, which had been 
presented by kim to the Museum of Trinity College, Dublin. 
A new TInitellular Epiphytic Green Marine Alga, exhibited . — 
Dr. E. P. Wfight showed specimens of a new unicellular epi- 
phytic green marine alga found attached to larger forms in rock- 
pools at Howth. This was a sub-globose or balloon-shaped, or 
sub-quadrilateral thick-walled, form often showing empty cells still 
attached by tleir lower extremity, their contents evacuated as 
zoospores. Tius this would be to a great extent like Characium, 
but the forms there included are stipitate. It called to mind a 
form found bf Mr. Archer some few years ago in moor-pools in 
Connemara aid attached to confervoids, but the cells were cubical, 
thus presentiig a quadrilaterul outline and the examples attached 
(sometimes ii rows) by the whole of the base in it, forming the 
longest diamder. 
Roothairs inside the rootsheaths in Azolla pinnata . — 
Dr. McNab exhibited roots of Azolla pinnata, showing the 
sheath with the numerous root-hairs developed inside the inner 
sheath, and leld down by it with their apices pointing to the 
apex of the loot until they are liberated by the elongation of the 
root. Thes« hairs are produced in regular whorls close to the 
growing-poirt, but by growth of the axis their regularity is 
disturbed. Strasburger mentions that in Azolla pinnata the 
sheath breiks up and gives the root a plumose appearance. 
Nothing life this could be observed either in young roots or in 
those whidi have lost the root cup. As Strasburger does not 
describe ary root hairs on these plants, it is probable that they 
have beenoverlooked. 
Micrasirias furcata, exhibited. — Mr. Archer showed an example 
of Micraierias furcata, one of the most rare as well as the most 
beautiful of the Desmidiem. He had himself seen probably in 
all not Hlf a dozen examples of this fine species, always from 
Connema’a, and which appears quite distinct from M. Crux- 
Melitenis, itself very rare, but cropjiing up sometimes, mainly in 
CO. Wesimeath gatherings. 
Tricim fallax, exhibited. — Mr. Greenwood Pirn showed Trichia 
fillax, /ar. cerina, from his stove at Monkstowii. This form 
(lifiers Torn T. chrysosderma in having much finer and more 
delicaU spiral elaiers, which are cylindrical and taper abruptly 
