320 PHYSIOLOGY OF NUTRITION. 



either in the cells of the outer green layer of the ovary or of the 

 inner colourless layer. Only in the immediate neighbourhood 

 of the vascular bundles in the ventral and dorsal sutures is a 

 small quantity of starch present. The embryo sac contains no 

 starch (perhaps owing to its being very rapidly used up). 

 Starch is, however, present in the neighbourhood of the embryo 

 sac and in the parenchyma of the funicle. When the fruit has 

 attained a length of 3 cm., the outer green layer of the ovary 

 contains starch ; the inner colourless layer contains no starch, but 

 much sugar. In the funicle, and in the immediate neighbourhood 

 of the embryo sac, starch is present. The embryo, which is still 

 very small, is devoid of starch. As the development of the fruit 

 and seed proceeds, much starch (but no sugar) is still always to 

 be found in the parenchyma of the funicle, which serves as an 

 organ of conduction, and also a large quantity of starch gradually 

 accumulates in the cotyledons of the developing embryo. 



Cases have come before me in which neither in the embryo sac, 

 nor in the tissue of the nucellus and funicle (presumably in con- 

 sequence of the very active growth of the cells), were starch or 

 sugar to be detected. I investigated on May 4th flowers of 

 Tulipa sylvestris, and found in the cells of the anatropous ovules, 

 contained in large numbers in the trilocular ovary, large quan- 

 tities of proteid, but neither starch nor glucose. 



See Sachs, Pringsheim's Jahrblicher, Bd. 3, p. 231. 



128. Preparation of the Material Necessary for Quantitative 

 Chemical Researches on Metabolism. 



One of the most important but at the same time most difficult 

 and tedious tasks in quantitative chemical investigations concern- 

 ing plant metabolism is to obtain suitable material. It is best to 

 use seedlings in such observations, e.g. in studying the behaviour 

 of starch or fat. We first endeavour to procure seeds of uniform 

 development, and also thoroughly capable of germination, deter- 

 mine the weight of dry substance they contain, obtaining an 

 average value by drying at 102 C. several samples of the powder 

 obtained by grinding the seeds in a hand-mill, and calculate all 

 the results of the researches in terms of dry seed substance. 



The seeds to be used for obtaining seedlings must be accurately 

 weighed ; the weight of dry substance they contain is then easily 



