January 29, 1915] 



SCIENCE 



175 



The Nature of Mechanical Stimulation: W. J. V. 



OSTEBHOUT. 



The chief difficulty whieli a theory of mechan- 

 ical stimulation must meet is the production of 

 chemical reactions by a mechanical disturbance. 

 This diESeulty is met by supposing that the me- 

 chanical disturbance breaks down semipermeable 

 surfaces, thus allowing substances to react which 

 were previously kept apart. Experimental evi- 

 dence is brought forward in support of this view. 

 Studies in Plant Oxidases: G. B. Reed. 



1. Evidence for the General Distribution of the 

 Oxidases. — Some algae which have been reported 

 to be without oxidases were found to contain a 

 ferment capable of activating the oxidation of a 

 specific group of compounds. 



2. The Formation of Indophenol Granules. — 

 Indophenol granules were found to form in cells 

 which had been killed by agents which do not 

 affect oxidases, but did not form in cells killed by 

 agents known to destroy oxidases. 



3. On the Separation of Oxidase Seactions from 

 the Caralase Beaction. — By subjecting colloidal 

 platinum to active oxygen at an anode its oxidase 

 activity towards gum guaiacum and potassium 

 iodide was increased, while its catalase activity was 

 decreased; and by treating with active hydrogen 

 at a cathode the opposite effects were produced. 

 Bright platinum after anodic oxidation has a defi- 

 nite oxidase action, but no catalase action. Some 

 plant extracts were found which contained oxi- 

 dases, but no catalase. 



4. An Acid-stable Oxidase. — While the oxidases 

 are ordinarily inhibited by a slight degree of 

 acidity, an oxidase was obtained from pineapples 

 and some other fruits capable of withstanding 

 0.1 M. HCl. 



Enzymes of the Marine Algcs: A. E. Davis. 



Continuing the work begun with Fucus, isola- 

 tion and identification of enzymes occurring in 

 representative marine forms of the greens, browns 

 and reds has been carried on. The results ob- 

 tained show certain differences for the different 

 groups of algaa: carbohydrases attacking the 

 various polysaccharides are generally distributed 

 in the greens and reds; when present in the 

 browns they are much less active, and in a few 

 genera have not yet been detected with the meth- 

 ods used. Compared with potato leaf tissue pre- 

 pared in the same way, the earbohydrase activity 

 of Viva lactuca, the most active form studied, was 

 about half, 

 o Proteinases acting upon albumin, legumin and 



peptone in neutral and alkaline solution were iso- 

 lated from the majority of the forms worked with 

 and, as was true for the carbohydrases, were most 

 active in certain of the greens and reds. No 

 amidase action was observable. 



With the exception of a few forms lipase was 

 found to be very generally present, being especially 

 active in Chondrus and Desmerestis ; on the other 

 hand, fatty esters were not acted upon. 



Oxidases and peroxidases were foimd in but 

 one form — Agardhiella. In this both were quite 

 active, comparing favorably with potato tuber 

 tissue. Catalases were present in all forms. 



The total number of enzymes isolated was small 

 when compared with the tissues of the higher 

 plants, and their action decidedly slower. In gen- 

 eral this action was greater in the greens and the 

 reds than in the browns. 



Concerning the Measurement of Diastase Activity 

 in Plant Extracts: Chas. 0. Appleman. 

 Several methods have been proposed for the 

 measurement of the velocity of diastase activity 

 in plant extracts. The procedure adopted by sev- 

 eral investigators is based upon the determination 

 of the amount of reducing sugar, usually calcu- 

 lated as maltose, produced by the action of a defi- 

 nite amount of extract upon an excess of soluble 

 starch for a definite length of time at constant 

 temperature. The Kjeldahl "law of proportion- 

 ality" is sometimes observed and sometimes ig- 

 nored. The general inapplicability of this method 

 for plant extracts is very strikingly shown in the 

 following table, which refers to the diastase activ- 

 ity in glycerine extracts from cold storage pota- 

 toes: 



TABLE I 

 Increase in Milligrams of Sugar at 40° C. Per 

 Hour Per 100 GrftHiB of Potato Pulp 

 Date of Total Reducing Sujar Total 



Analysis Calculated as Maltos* Sugar 



November 28 17.0 3.6 



December 20 24.6 3.7 



January 13 81.9 3.7 



Calculated on the basis of increase in total re- 

 ducing sugars or maltose in the extract after incu- 

 bation with soluble starch, the tubers would show 

 a very marked increase in diastase with storage, 

 but when calculated on basis of increase in total 

 sugar, the diastase activity remains practically 

 constant. The amount of sucrose in the tubers 

 in.creases with cold storage. It is extracted with 

 the diastase and is inverted at the incubation tem- 

 perature, according to the law of the mass action. 



