STARCH IN GERMINATING PEAS 179 



tributed throughout the cotyledon, or does it exist only in the peri- 

 pheral layer or layers of cells? To answer these questions several 

 experiments were performed. 



Experiment 1. Dried peas were ground, and treated with 

 concentrated glycerine. After standing for about an hour, the 

 mixture was filtered. Some of the filtered extract was added to 

 a thin starch paste, and kept at 50°C. The starch was soon 

 changed to sugar, showing that active diastase had been extracted 

 without any contact of the living protoplasm with water. 



Experiment 2. Pea testas, removed from the dried seeds, were 

 ground and extracted, both with glycerine and with water. When 

 tested with starch paste, both the glycerine and the aqueous extracts 

 showed diastatic activity, thus demonstrating the presence of 

 diastase in the testa. It is of interest to note here that Wohllebe, 9 

 in his work on the enzyme content of the various parts of seeds, 

 obtained no diastatic secretion from the testa of Pisum sativum. 



Experiment 3. The peripheral layer of cells was removed from 

 the cotyledons by means of a file. The filings were extracted 

 with water, and the extract tested with starch paste. A diastase 

 was present. 



Experiment 4- Peas, from which the testas had been removed, 

 were soaked in water for about five minutes, and the softened 

 outer layer scraped off. An aqueous extract of this softened 

 mass showed the presence of a diastase. 



Experiment 5. Material from the interior of the cotyledon was 

 obtained by breaking the cotyledons of dried peas, and drilling 

 into the broken surface with a dental "burr." The powder so 

 obtained was treated with water," and the diastatic action was 

 obtained with the extract. 



It is seen then, from these experiments, that an enzyme, or 

 possibly a zymogen activated by water, is present throughout 

 the cotyledon and in the testa. It is also clear that this enzyme 

 is not formed by the action of the water of imbibition on the living 

 protoplasm. Is it possible, however, that the water of imbibition 



9 Wohllebe, H., Untersuchungen iiber die Ausscheidung vondiastatischen und 

 proteolytischen Enzymen bei Samen und Wurzeln. Diss. Leipzig, 1911. 



