374 
SUMMARY OF CURRENT: RESEARCHES RELATING TO 
Respiration of Plants.* — Herr W. Detmer finds, in tlie case of 
wheat, that the optimum temperature for respiration is between 35 3 and 
40' C., the minimum being below zero. Respiration ceases with death, 
any production of carbon dioxide after this being due to the presence of 
bacteria. When oxygen is excluded, an active decomposition of the 
albuminoids takes place, the resulting products being amides and amido- 
acids. 
Respiration and Fermentation of Yeast. t — MM. Grehant and 
Quinquad find, from a long series of experiments, that notable quantities 
of gas are included in yeast, especially carbon dioxide and nitrogen. When 
yeast respires at a temperature between 8° and 15° C., the quantity of 
carbon dioxide produced is less than the quantity of oxygen absorbed, or 
the proportion 
CO 
0 
— is less than unity. 
Respiration does not cease even 
at zero, and the proportion becomes then nearly unity. At a 
CO, 
temperature between 15' and 18", the value of „ ' is unity or higher ; 
at 40~-50” it reaches two or more ; one of the effects of a high tempera- 
ture is to increase the production of CO*. The respiration of yeast 
decreases in intensity when the temperature of the atmosphere is above 
QQ 
50', and the proportion ——?■ falls again below unity. In the entire 
absence of oxygen, yeast can produce large quantities of carbon dioxide, 
borrowing the elements from its own tissue. Yeast absorbs the same 
quantity of oxygen when it produces fermentation as when it respires 
under simple conditions without fermentation. Fermentation can 
proceed rapidly in a vacuum with a temperature of 40°. 
Lactase, a new Enzyme. i — According to Herr M. W. Beyerinck, 
there are two ferments which ferment sugar of milk, Bacillus caucasicus , 
which exists in Kefyr, and a Saccha ram yces, which he names S. tyrocola , 
which is found in Edam cheese, and which has been erroneously identified 
with S. - ± and with .S’. Kefyr ; it differs from the latter in its form, 
being more nearly allied to S. lactis. He states that the fermentation is 
effected by a diastase distinct from invertin, which he calls lactase. It 
has no effect on the luminosity of Photobacterium phosphorescens, while 
glucose and galactose increase its luminous property. The invertin of 
S. ellip&oideus has no effect on sugar of milk, while S. Kefyr and 
S. tyrocola produce a diastase which inverts that sugar. 
Nitrifying Process and its Specific Ferment! — Prof. P. F. and Mrs. 
G. C. Frankland have made an investigation into the process of nitrifi- 
cation, the principal results of which are these : — They have succeeded, 
by the method of fractional dilution, in isolating a micro-organism 
present in ammoniacal solutions which were undergoing a nitrification 
which was originally induced by a minute quantity of garden soil. 
This organism is a very short bacillus, about 8 p long, hardly longer 
* Ber. Dentsch. Bot. Gesell., viii. (1890) pp. 226 -30. 
+ Ann. Sc-i. Nat (Zool.). x. (1890) pp. 269-328. 
X C'entralbl. f. Bakteriol. u. Parasitenk.. vi. (1890 p. 44. 
§ Phil. Trans., 181 B. (1891) pp. 107-28. 
