METABOLIC PROCESSES IN THE PLANT. 



297 



starch, as was shown by means of the Iodine reaction. Since, 

 however, such material does not contain nearly so much diastase 

 as barley seedlings, it is advisable to use very dilute starch paste, 

 and add only very small quantities of it (perhaps 2 c.c.) to a 

 fairly large quantity of the plant extract. 1 2 



To prepare the diastase-containing extracts, the plant structures 

 are cut up, pounded with a little water in a mortar, and placed in 

 from two to four times their volume of water for two to six hours. 

 \Ve then filter. Proceeding in this way we can certainly discover 

 the ferment in plant structures if it is present in good quantity. 

 The method is not, however, suitable for small quantities of dias- 

 tase, and hence Wortmann's conclusion that many kinds of foliage 

 leaves, for example, in which he could detect no diastase by that 

 method of treatment, contain no ferment capable of isolation. 

 The solution of the 

 starch would then be 

 brought about directly 

 by the protoplasm. This 

 may be true in some 

 cases; Brown and Morris, 

 however, have recently 

 pointed out that in many 

 cases the treatment of 

 fresh plant structures 

 with water for extrac- 

 tion of diastase is not 

 to be recommended at 

 all. It is not easy to 

 crush all the cells of 

 these fresh structures, 

 so that the extraction is incomplete, and in testing for diastase 

 a negative result may be obtained, although the ferment actually 

 occurs in the structures. We obtain much more trustworthy 

 results if we first dry the material at about 40 C., then rub it 

 down very finely, and now add the powder obtained, or an ex- 

 tract of it, to starch paste. It is found in this way that even 

 many foliage leaves are very rich in diastase, as I satisfied myself 

 in the case of foliage leaves of Pisum sativum. 3 



\Vith reference to the action of diastase in plants, it is very im- 

 portant to satisfy oneself that the ferment can act upon and dis- 

 solve not only starch paste, but even uninjured starch grains. To 



FIG. 109. Starch grains from the endosperm of a 

 wheat grain in different stages of corrosion, a, 

 slightly corroded ; b, more deeply corroded ; c, morfl 

 deeply still; d, most strongly of all. (After Bara- 

 netzky.) 



