658 SUMMARY OF CURRENT RESEARCHES RELATING TO 



also live at a temperature of — 19 '3°. It is shown that this alga, when 

 removed from this normal habitat and cultivated at an ordinary dwelling- 

 room temperature, gradually loses its power of resisting heat ; and this 

 becomes the more marked in proportion to the length of time it is 

 cultivated in cool water. 



Osmotic Properties of Cells of Cyanophyceae.*— F. Brand details 

 the results of certain experiments in this direction and sets them under 

 three headings. (1) Reaction to plasmolysing solutions ; (2) reaction 

 to pure glycerin, glycerin saturation ; (3) " plasmoptyse, 1 ' the effect of 

 sudden irrigation with water on a cell which has just been deprived of 

 its watery sap by glycerin. 



Petalonema alatum.f — Daisy S. Hone has examined material of 

 this alga collected from the gravel bed of a quiet stream in Minneapolis, 

 where it formed a dark chestnut-brown stratum. The colour is due to 

 the gelatinous sheaths in which the trichomes are imbedded. The 

 pseudocysts are very variable in size and shape. The heterocysts are 

 solitary and interstitial, somewhat globose or oblong, slightly larger than 

 a normal pseudocyst. 



Water-Bloom 4 — N. P. B. Nelson has studied the subject of this 

 occurrence in Minnesota and neighbouring States, and finds that it may 

 be formed by seven different species of Cyanophyceae, namely, Glceo- 

 trichia pisum Thur., Coelosphcerium kuetzingianum Naeg., Apliani- 

 zomenon flos-aqua Ralfs, Clathrocystis aeruginosa Henfr., Anabccna 

 circinalis Rabenh., A. flos-aquce Breb., and A. mendotm(?) He finds 

 that the presence of one or more of these species in water drunk by 

 cattle often causes fatal results. 



Perforating Alga3.§ — G. Nadson passes in review the principal 

 types of this group of alga?, and expresses the opinion that they play an 

 important part in nature, by facilitating the disintegration of rocks and 

 stones. He believes that Conchocelis rosea Batt. is a variety of Ostreobium 

 Queketti. 



Anabsena.|| — E. Lemmermann describes a new variety, marchica, of 

 Anabcma cylindrica Lemm., from Langer See in Brandenburg. It is 

 distinguished from the type of the species by its larger size and the 

 absence of the colourless empty cell-wall surrounding the heterocysts. 

 The differences are shown in the form of a table and a key is given 

 which includes four other species having cylindrical cells, as well as A. 

 cylirtdrka and its new variety. 



Calcareous Pebbles. % — C. Powell describes some calcareous pebbles 

 found in Clearwater Lake, Wright county, Minnesota. They were found 

 lying on sand-bars in water from 4 to 10 feet deep, and they range 

 in size from that of a small hickory nut to ^ in. in diameter. All 



* Ber. Deutsch. Bot. Ges., xxi. (1903) pp. 302-9. 



t Minnesota Bot. Studies, iii. (1903) pp. 47-50 (1 pi.). 



j Tom. cit., pp 51-6 (1 pi.). 



§ Script. Bot. Hort. Univ. Petrop., xviii. See alsoNuov. Notar.,xiv. (1903) p. 141. 



|| Hedwigia, xlii. (1903) Beibl., pp. 168, 9. 

 i Minnesota Bot. Studies, iii. (1903) pp. 75-7 (2 pis.). 



