è08 



crystalline structure. Jacquelain liiuiself, who first mentioned tiiesé 

 grains, called tliem "granules de tecule". ') 



After having become acquainted with the described facts and 

 found them confirmed for other species of starch, I convinced myself 

 that the natural starch grain also is built up of crystal needles 

 radiating from the dot or hilum. This may best be seen in soluble 

 potato starch, very cautiously heated in the microscopic preparation 

 on the slide under the coverglass, when all the stages of the dissolving 

 in hot water can be followed. The tiny radiating crystal needles 

 then become visible in a ring-shaped arrangement, such as might 

 be expected from the structure of the starch grain itself. It seems 

 that the length of the needles corresponds with the thickness of the 

 rings. 



From the preceding I conclude, that the formation of tiie starch 

 grain takes place in the following way. The amyloplast produces 

 granulose, which in the interior crystallises to small spherites, just 

 as in a solution. But this granulose production occurs periodically, 

 and so the process of crystallisation gives rise to the formation of 

 the layers of the grain. 



To explain the great difference existing between starch gelatinised 

 at 100° C. and that heated to 150' and 160' C. it must be accepted 

 that in the starch grain, beside the granulose, an incrustating 

 substance exists, functioning as a "protecting colloid", whose presence 

 makes the needles remain short, the shorter the more of the colloid 

 is present. It remains active unto about 100° C, but above 

 this temperature it slowly decomposes, quite to vanish at about 

 1 50° C. 



The hypothesis that this protecting colloid might be a phosphoric 

 ester of granulose,- is contrary to the properties of soluble starch, 

 for this behaves at crystallisation of the solutions, prepared between 

 100° and 150° C, precisely in the same manner as natural starch 

 so that the protecting colloid is still present in this substance, whereas 

 it might be expected that an ester would be decomposed by the 

 strong, 107o-ic hydrochloric acid used for its preparation. 



Perhaps the colloid is the amyloplast itself, which, at the formation 

 of the starch grain, remains partly enclosed between the fine granulose 

 needles. Its greatest accumulation would then occur in the amylo- 

 pectose wall of the grain, which does not yet dissolve at boiling. 



M J A. Jacquelain, Mémoire sur la fécule. Annates de Chimie et de Physique. 

 T. ü3, I'ag. 173, Paris 1.S40. Much in lliis treatise is incorrecl and obscure, else 

 the (iisfs would certainly already earlier have drawn general attention. 



