PROCESS OF STORAGE 1 85 



Sometimes it happens that the starch begins to be deposited at 

 more than one point in the leucoplast, so that two or more rela- 

 tively small grains become closely associated, and adhering with 

 more or less tenacity they constitute a compound grain (Fig. loi). 



In storage tissues, where simple grains are the rule, com- 

 pound grains may also occur; and in some instances, as in oats 

 and rice, compound grains are the rule. 

 In some cases small units of starch may 

 begin to form a compound grain and 

 then all become encased in a common 

 starch sheath deposited by the exterior 

 part of the leucoplast. These grains 

 are called half-compound. F'g- i 01. —showing con- 



centric 3.Tid excentric stri3.~ 



The storage of oils and fats takes tions of starch grains, e, 

 place in the vacuoles and throughout p°^^^° ^f ""^^ excentricaiiy 



^ '^ striated; /, compound starch 



the meshes of the cytoplasm, and it grain from potato; g, bean 



, . e- 1.1..1 .1 1 starch concentricallv striated. 



may be mferred that the cytoplasm has 



more to do with their construction and storage than have the 

 other cell organs; but the mere fact that reserve food occurs in 

 a certain cell organ is not to be taken as evidence that other 

 cell organs have not cooperated in its manufacture. 



In following the ripening of oily seeds it is found that sugars 

 and starch are present in the immature seeds, but little or no 

 oil. As ripening proceeds, however, oil appears and gradually 

 increases in amount, while the sugars and starch disappear, 

 having unquestionably contributed the elements for the con- 

 struction of the oil. 



In the leaves of Vanilla and other Monocotyledons have 

 been found rounded bodies containing oil in their meshes, and 

 these bodies have been supposed to be oil formers and have 

 been named elaioplasts (Gr. elaion, oil, and plassein, to form). 



Reserve sugar occurs in solution in the cell-sap of the stor- 

 age cells, and it probably exists within the cell wherever the 

 cell-sap penetrates. There is no special cell organ devoted to 

 the storage of sugar, and whether the cytoplasm is most active 

 in this process has not been determined. As has been stated. 



