196 SUMMARY OF CURRENT RESEARCHES RELATING TO 



functions as an embryo-sac when the true embryo-sac does not develop. 

 The true embryo-sac has no antipodal cells and no antipodal polar 

 nucleus ; it undergoes little development after the formation of the 

 egg-apparatus, so that no endosperm is formed. The development 

 favours the view that " the egg-apparatus of the higher plants is a 

 reduced archegonium." 



Physiology. 

 Nutrition and Growth. 



Rise in Temperature of Foliag-e-leaves.* — H. Molisch has carried 

 out experiments upon Carpinns Betulus, Salix Caprsea, Gytisus 

 Laburnum, Abies excelsa, Solanwn tuberosum, Brassica, etc., with the 

 view of investigating the causes which produce rise in temperature in 

 living, freshly plucked leaves. Leaves of Monocotyledons, evergreens, 

 and similar plants show very little increase in temperature ; tubers and 

 such fruits as those of Pints communis behave in the same way. 

 Generally, however, freshly plucked leaves when heaped together and 

 protected from draughts and excessive transpiration behave similarly 

 to buds and germinating seeds with respect to increase of temperature. 

 Such leaves quickly reach a maximum temperature, and if the experiment 

 is stopped after 12 to 15 hours, just before the maximum temperature 

 is reached, the leaves are stil quite fresh. Examination shows that 

 bacteria or fungus-spores have little if anything to do with this first 

 increase in temperature, which must therefore be entirely due to 

 respiration of the leaves. When the maximum temperature is reached, 

 the leaves die and bacteria and fungus-spates rapidly germinate, 

 producing a second rise in temperature which may be even greater 

 than the maximum temperature reached at first. Finally the tempera- 

 ture again falls until it reaches that of the room. The action of the 

 germinating spores, etc., together with that of enzymes and chemical 

 processes, are doubtless responsible for the second rise in temperature. 

 The above results are not obtained with wet or submerged leaves. 



L ^ v 



Reversing* Currents in Plasmodia of Mycetozoa.f — A. E. Hilton 

 has studied the streaming movements in the plasmodia of Badhamia 

 utricularis, and draws the following conclusions from his observations. 

 The currents in the larger veins control the movements in the finer 

 threads. The main currents in the large veins radiate from and 

 converge to definite centres. Removal of these centres causes diminu- 

 tion and disorganisation of the streaming, but in a short time the 

 denser portion of the remaining mass forms a fresh centre, and streaming 

 is renewed. If two separate portions of a plasmodium coalesce, one or 

 other of the two main centres acquires predominance and controls the 

 streaming of the whole. When one large plasmodium has more than 

 one centre of control, severance takes place at the limits of control of 

 each centre unless harmony is established. A certain relative proportion 

 must be maintained between the mass of the controlling centre and that 



* Bot. Zeit.,lxvi. (1908) pp. 211-33(2 figs.). 



t Journ. Quekett Micr. Club, ser. 2, x. (1908) pp. 263-70. 



