276 
Notes . 
Water-lily House, Victoria Regia House) this periodicity is observable. 
Desmids and other Conjugates are very rare before April, although 
some of the unicellular Protococcoideae are here to be found all the 
year round. 
Much has already been written about the periodicity in the develop- 
ment of certain Plankton organisms, but little attention in this respect 
has been paid to those inhabiting the deeper strata of the water. In 
all the artificial waters at Kew a regular sequence of forms was 
observed; it was most pronounced in the aquatics’ tank near the 
Jpdrell Laboratory, in which, by the removal every now and then 
of the mass of Algae that collects there, room is constantly being 
furnished for the development of other forms. Table I (see next 
page) illustrates this periodicity in the algal flora very well. 
A careful perusal of this Table will show that the flora in any one 
month differs more or less considerably in character from that of the 
preceding or succeeding month. Undoubtedly the removal of the 
large masses of Algae, which collect in the space of every fortnight 
during the summer, considerably furthers this periodical development. 
Thus a little time after the tank had been thoroughly cleaned out, 
I met with the curious red oospores of Sphaeroplea annulina , a species 
which had been found in abundance in this tank in a former year, but 
had since not been observed. These oospores had probably been 
liberated during the cleaning-out of the tank, and in a few weeks gave 
rise to a large number of vegetative filaments of the Sphaeroplea. 
However, even in the lake, where no such artificial agency comes 
into consideration, the periodicity of the flora is well marked, as will 
be seen by Table II (see next page). 
Enteromorpha intestinalis, Tetraspora gelatinosa , and Oscillaria nigra , 
all very abundant in the summer months, especially the first and last 
species, are entirely absent in the early part of the year ; they thus 
give the algal flora of the summer an entirely different stamp to that 
of the winter. In addition to this we may note the development of 
the Desmidieae, which is, however, relatively poor in the calcareous 
waters of Kew, as already mentioned. 
Oscillaria nigra also played an important part in the water- 
lily pond. In the earlier part of the year a Cladophora was 
the most abundant form here, and no trace of the Oscillaria 
grossen u. kleinen Seen, Zoolog. Anzeiger, Bd. xxii, Nos. 577 and 578, 1899, 
p. 19, &c.). 
