75 
SOME FRESH WATER ALGtM. 
Fungi are sometimes said to be very erratic organisms, but I 
doubt if tbeir uncertainties are much greater than are found 
amongst the Fresh Water Algas. In the past summer, quite 
unexpectedly, the very beautiful water-net ( Hydrodictyon utricu - 
latum ) was found floating in a small pond in the pleasure 
grounds of Kew Gardens in such profusion that a barrowfull 
might soon have been collected. In three weeks another visit was 
paid to the same spot, in order to obtain some specimens for exhibition, 
and not a vestige could be seen on the surface. They might have 
gone to the bottom, but practically they were not obtainable. No 
one appears to have ever recognised the plant in this pond before, 
and possibly it may not be found again. 
Passing through the propagating houses nearly at the same 
period of the year, the moss, which was growing freely on the 
damp walls, was observed to be encrusted with a glaucous Alga, 
not yet, as far I know, recorded as British. This was the species 
called in Rabenhorst’s “ Flora” Scytonema cinereum, variety Micheli, 
which is the Dnlosiphon muscicola of Kutzing. It was such a 
prominent object that one could scare avoid feeling surprise that it 
should never have been recorded. 
Passing on another occasion the large pond in the pleasure 
ground, I noticed some globose olivaceous tufts of an Alga float- 
ing freely in the water or attached to small fragments of dead 
grass. The tufts were about the dimensions of a marble. Finding 
myself in some doubt as to its determination, I sent specimens to 
Professor Nordstedt, the result being that he came to the conclu- 
sion that it was the species which Dr. Kirchner had included in 
his “ Schlesischen Algen ” under the name of Plectonema mira- 
bile, as of Thuret, but which did not, from the dimensions, appear 
to be Thuret’s species. The threads were very nearly the size of 
those given by Dr. Kirchner, and if not his species, it will come 
very near to it. If this assumption proves correct, the species will 
stand as Plectonema Kirchneri , whilst Thuret’s name of Plectonema 
mirabile will still be retained to represent the old Calothrix mira- 
bilis, Agardh, which is certainly distinct from the Kew specimens. 
Apropos of new species, a minute green, filamentous Alga has 
been found in some five or six localities with a small radius in 
Yorkshire, which for some time has proved a puzzle, and even yet 
has not perhaps found more that a temporary location in the genus 
Microthamnion , much more delicate than either M. strictissimum or 
M. Kutzingianum, which for the time we have been content to call 
Microthamnion vexator. The figure 107 in Rabenhorst’s “ Algas ” 
(p. 302) is much more like our plant than it seems to be of M. 
strictissimum , supposing it to be magnified about 320 diameters. 
Professor Wittrock, to whom the plant has been submitted, does 
not recognise it as any described species, and suggests for it a 
location in the above-named genus. 
M. C. C. 
