In calm weather the waters of Lake Ontario hold very little visible sediment in suspension. They are, moreover, quite free fronm any discoloration of organic matter such as that which gives a yellowish green tinge to the large, lakes of Manitoba and of some other parts of the North-west. The water of Lake Ontario may be described as very clear and showing for lake waters a maximum freedom from suspended matter. In the clear waters of this lake, those forms of algae which require only a moderate amnount of light might be expected to extenld their habitat to a considerable depth. It is not surprising therefore that specimens of a Cladophora were obtained last summer from a depth three times greater than had been previously recorded for it. The fishermen who set their nets in the deeper waters of Lake Ontario very frequently bring to the surface slabs of limnestone which they call honeycomb rock, a natme suggested by the extraordinary appearance of the surfaces of these specimens, which are deeply pitted by irregular cell-like cavities. Many of these specimens, a series of which was secured during the last field season by Mr E. J. Whittaker, while engaged with mie in studying bottom conditions in Lake Ontario, came from a depth of 150 feet, 16 miles s.w. of Presque Isle in Lake Ontario, entirely covered by a growth of green algae. Some of these were sent to Mr Frank S. Collins, a specialist on this class of planits, for determination. Mr Collins writes (Dec. 22, 1914) concerning these as follows:- have received the specimens of a Cladophora that you collected in deep water in Lake Ontario; it is an interesting collection, being from a greater depth than recorded for any Cladophora and the plant is certainly a species not hitherto recorded for America. think it is C. profunda Brand, found in the lakes of the Bavarian highlands, at a depth of 15 metres, but it differs somewhat from that species, so have sent some to Prof. Brand for him to decide whether it is distinct. A second letter (Feb. 15, 1915) from Mr Collins after hearing from Prof. Brand follows: I have heard from Dr Brand in regard to your Cladophora, and the following is a tianslation of his letter. 'The Cladophora is indeed C. profunda, a slender and irregularly branched form, which may be characterized as forma ina of variety Nordstedtiana. Irregularities are very commion in C. profunda, and arise from the