PUENOMENA OF DIGESTIBILITY— RAW STARCHES. 189 



the development of the pore-canals. This is very often accompanied by the formation 

 of an inner cavity. In all such cases the starch dissolves from within, as is usually observed 

 in the smaller grains. 



The characteristics marking the processes of erosion in Lilium candidum, Lalhrcca 

 dandcstina, Orobanchc, and Phaius grandijlorus may be grouped as follows: (1) Erosion 

 usually takes place from the outside; (2) in large grain special local points of erosion often 

 occur in the form of grooves or crater-like depressions; (3) in contradistinction to the above, 

 the small grains usually tlissolve from within, inasmuch as pore-canals are developed which 

 by extending to the inner i^art of the grain often produce a cavity. 



Erosion of Starch-Grains in Non-Typically Reserve-Storing Parts of the Plant. 



In parasitic plants like Neoitia nidus-avis and different species of Lalhrcca and Oro- 

 hanchc, during the de\elopment of the buds a large amount of starch develops in the cells 

 of the flower-stalks. As soon as fructification has taken place and the seed begins to 

 develop, tins starch disappears from these parts in the same way as from the true reserve 

 receptacles. In the rather small grains of Neoitia 7vidus-airis the grains are usually attached 

 by pore-canals and are broken by ramification of the same. In Lalhrcca and Orobanche 

 the process is as previously described. In non-parasitic plants, as well as in those having 

 oilj' seeds, such as Linnm raphanus, Sinapis, Papaver, etc., the same erosion character- 

 istics appear in more or less marked degree. 



Erosion of Starches Outside the Plant by Action of Watery Extracts 

 OF Diastase and by Bacterial Fluids. 



Baranetzky (page 181) has recorded that most starches dissolve outside the plant in 

 watery solutions of diastase, and Wortmann (page 186) has proved that bacteria are capa- 

 ble of attacking starch-grains. In Graminacece Krabbe found that erosion is alike in 

 germinating seeds in extracts of diastase and in bacterial fluids. Slight deviations were 

 noticed in the bacterial fluids. In potato starch, on the other hand, the process of erosion 

 in extracts of diastase and in bacterial fluiils differs from that in sprouting tubers. Uni- 

 form dissolution of the grains from without, which is a rule in tubers, seems never to take 

 place outside the plant in extracts of diastase or l)acterial fluids. In the bacterial fluid the 

 starch-gi'ains develop depressions like holes bored into the outer surface of the gi'ain, and these 

 depressions increase in circumference and depth with the continued action of the bacteria; 

 they naturally merge into each other as the starch-substance separating them gradually 

 '.lissolves, thus producing large irregular depressions on the outside of the grain. Tlie action 

 of extracts of diastase outside the plant produces superficial irregular points of erosion which 

 soon deepen and enter the inner part of the grain and assume different forms. As a rule, the 

 eroded grains are filled with a network of canals, and inner cavities are also usually formed. 

 Sometimes superficial fissures have been obser\'ed in the diastatic action in the grains of 

 potato starch, the ramification of which gave the grains a reticulated appearance. Such 

 branched fissures were observed in the eccentric and distinctly lamellated grains of Frilillaria 

 imperialis. The fissures begin at the wide end of the grain and lengthen and ramify until 

 they completely cover the outer surface. As they lengthen they also become deeper, and 

 if the diastase is allowed to act long enough they finally cut the grains into pieces. 



Day {loc. cit.) observed the effects of unfiltered saliva on potato, arrowroot, corn, 

 rice, wheat, and barley starches. After 14 hours at 40° (the preparations each containing 

 a few drops of thymol solution) in most of the corn and rice grains the center part was 

 apparently all dissolved, leaving a thick shell having deep clefts along what were the etlges 

 of the polyhedral grain; in many of the barley and wheat grains there was no change 

 except corrosion of the surface, but in many others there remained nothing but hollow 



