THE STRUCTURE OF THE STARCH GRAIN.' 



Henry Kraemer. 



(with plate XI AND TEXT FIGUREsl 





There have been a number of hypotheses advanced to explain 

 the origin, nature, and structure of the starch grain, (i) It was 

 originally considered to be a bubble filled with a liquid, or, as 

 stated by Nageli, " einer mit Flussigkeit gefiillten Blase/' 

 According to Von Mohl, Raspail considered that the starch 

 grain consists **aus einer in Wasser unloslichen blasenformigen 

 Hijlle und einem loslfchen gummiartigen Inhalte." (2) Then 

 (^834) it was considered that to a central or excentral point 

 layer after layer was added, the peripheral layers thus being the 

 last formed, this view having been advanced by Fritsche (i) 

 and supported in a more or less modified form by Treviranus (2), 

 Lindlej^ (3), Schleiden (4), Braun (5), Schacht (6), Criiger (7), 

 and Unger (8). (3) Payen (9) in 1838 conceived the idea that 

 growth took place from the outside, that through one or more 

 funnel-like openings at the periphery of the grain new substances 

 entered and new layers were formed therefrom, the outer layers 

 thus being the oldest, in contradistinction to the view advanced 

 by Fritsche. (4) Then followed a series of contributions in 

 which the growth of the starch grain w^as likened to that of the 

 cell wall and the formation of cells. This theory, with certain 

 modifications, was advocated by MQnter (lo), Walpers (ii), 

 Reissek (12), C. Nageli (13), Kutzing (14), and Hartig (15). 

 (5) While Nageli (16) recognized that assimilation starch arose 

 in plastids, he considered that most starch grains arose free in 

 the cell sap under the influence of living protoplasm, and it was 

 not until 1880 that Schimper (17) demonstrated that all starch 

 grains develop within plastids and that in the reserve starch 

 grains the leucoplastids finally disappear. Schimper further 

 showed that the outer portion of the grain is the youngest, 



'An abstract of a preliminary paper on this subject was presented to the Society 

 for Plant Morphology and Physiology, December 1899. 

 1902] 341 



