RECENT ADVANCES IN SCIENCE 575 



Helotium (Wakefield), Mycena (Pearson), Boydia, n.g. (L. 

 Smith), and Empusa (Cotton), are described in Trans. Mycol. 

 Soc. 



PLANT PHYSIOLOGY. By Franklin Kidd, D.Sc, Botany School, 

 Cambridge. (Plant Physiology Committee.) 



Respiration. — Professor Osterhout has recently turned his 

 attention to the study of respiration, and a series of papers 

 by him and by other workers associated with him under the 

 general title of Comparative Studies in Respiration are now 

 appearing in the Journal of General Physiology (vols. i. and ii.). 

 The raison d'etre for this series of studies is to be found in 

 the experimental method and apparatus used. These are 

 ingenious, and are stated to allow of rapid and continuous 

 measurements of extremely small quantities of C0 2 taken 

 in or given out by the plant tissues studied. The outline of 

 the method is as follows : a small quantity of tissue is placed 

 in a tube containing water and an indicator (and other sub- 

 stances in solution as the case may be), or the tissue is placed 

 in one tube and the indicator in another, a current of air being 

 circulated so as to bubble through both solutions. The 

 carbon dioxide evolved by the plant causes an increase in H-ion 

 concentration and consequently a change in the colour of the 

 indicator. An arbitrary interval in tint is chosen which by the 

 standard buffer mixture method can be expressed absolutely 

 as corresponding to a definite change in H-ion concentration. 

 The relation of the arbitrary change in H-ion concentration 

 chosen to the actual amount of C0 2 given out by the tissue 

 has not been attempted and is undoubtedly complex. It is, 

 nevertheless, clear that, other things being the same, variations 

 in the time taken to produce a definite though arbitrary change 

 in H-ion concentration correspond to variations in rate of C0 2 

 production. Moreover, if the rate of C0 2 production is rapidly 

 changing, the shorter the time intervals the closer will be the 

 correspondence. The smaller the arbitrary change in H-ion 

 taken as a basis the better. The order of change in these ex- 

 periments is from P* 7-60 to P fi 7-25, and the order of time 

 interval three minutes. To sum up, the method aims at 

 measuring the times taken for a tissue under observation to 

 give off arbitrary and unknown but small and equal quantities 

 of C0 2 . Changes in rate of respiration recorded are expressed 

 in percentages of the normal rate. The advance made is 

 that changes in rate can be followed practically from minute 

 to minute and in this way phenomena can be observed which 

 would completely escape notice in any method which requires 

 several hours for a single observation. Such methods only 



