274 SUMMARY OF CURRENT RESEARCHES RELATING TO 



Observations on Euglena deses. — Rose Bracher {Annals of 

 Botany, 1919, 33, 93-108, 9 tigs.). An account of the organism 

 that lives on the banks of the Avon, and is dependent on certain 

 external factors — light, tidal flow, and temperature. The influence of 

 light is direct and most important. The Euglense are visible upon the 

 mud during day-time, but burrow under the mud for the night, or when 

 placed in artificial darkness. The influence of tidal flow is shown by 

 the burrowing of the organism into the mud when covered by the tide ; 

 and the appearance of the organism is delayed or even prevented by a 

 mid-morning or early afternoon high tide ; also HJ. deses retains a tidal 

 periodicity for about three days after being removed to the laboratory. 

 The influence of temperature changes are less important, in that E. deses 

 is active at any temperature between 2-5° C. and 25° C. ; but beyond 

 these limits its movements are arrested. The optimum temperature is 

 about 15° C. Some of the figures show the shapes and positions 

 assumed during activity, at rest, and at night. A. G. 



Studies on the Chloroplasts of Desmids. I. — Nellie Carter 

 {Annals of Botany, 1919, 33, 215-54, 5 pis.). An account of the 

 chloroplasts of Netrium, Glosteryim, Tetmemorus, Eaastrum, Xanthidium. 

 Tlie general characters of the chloroplasts are summarized as follows : — 

 In the Saccodermre they are usually very simple in form. But in the 

 higher Desmids they are, in general, very complicated and beautiful 

 structures, and in many cases have not been previously investigated. 

 Their delicacy of form depends upon {a) the relative amount of 

 chlorophyll-bearing substance present in the individual, and {b) the 

 general physiological condition of the cell, particularly as regards the 

 quantity of free stroma-starch present in the chromatophore. The 

 chloroplasts may be asile or parietal, and their general form is usually 

 constant, but in a few cases there is marked variation in the disposition 

 of the chloroplasts amongst individuals of one species. The number and 

 position of the pyrenoids present depend on the size and shape of the 

 chromatophore. In the most extensive chloroplast plates of both axile 

 and parietal forms they are often very numerous and scattered. In all 

 cases the amount of food stored in the form of pyrenoids is dependent 

 on the condition of the cell, and at any time two or more pyrenoids may 

 be formed by the division of an original one. In many forms the 

 number of pyrenoids present in each semi-cell is generally supposed to 

 be constant ; but this is not true, since the actual number of pyrenoids 

 present is dependent on various changing factors, but in such cases 

 the points of pyrenoid formation are usually quite definite and fixed. 

 In addition to the ordinary large pyrenoids which are usually provided 

 with a starch-sheath, in several species numbers of small naked pyrenoids 

 or granules of protein were observed in the superficial layers of the 

 chromatophore. Summaries are also given of the special characters of 

 the chloroplasts in the five genera investigated. A. G. 



Studies on the Chloroplasts of Desmids. II.— Nellie Carter 

 Annals of Botany, 1919, 33, 295-004). An account of the chloroplasts 

 of Micrasterias. The summary of the results is as follows : — Normally 



