THE PLANT AND ITS FOOD. 9 



the storage of starch-grains in tubers, medullary 

 rays, roots, seeds, etc., obtained meanings not 

 understood before ; the spread of roots in the 

 soil, and the gradually discovered properties of 

 the finer rootlets and of the root -hairs, fitted 

 naturally into their places ; and, in short, a thou- 

 sand facts, otherwise isolated, became collated into 

 an intelligible system, full of suggestions for new- 

 work, such as has since gone on and is now being 

 pursued with an activity and success never before 

 realised in the history of science. 



As time went on, while the general truth of 

 Sachs' views was confirmed, a number of detailed 

 discoveries were made which seemed to contradict 

 them in certain points. It was found that not all 

 leaves form starch, for some contain sugar or oil ; 

 but Holle and Godlewski proved experimentally 

 that this oil may be replaced by starch if the con- 

 ditions of assimilation are slightly modified. More 

 recently Hebert discovered that the stalks and 

 leaves of grasses contain a peculiar form of gum, 

 which was formerly confounded with starch, a 

 substance not abundant in them. Then came 

 Schimper's discovery of starch-forming corpuscles, 

 which, if supplied with sugar, are able to form 

 starch-grains in the dark, as in tubers, etc., under- 

 ground ; and as subsequent researches have proved 

 that the chlorophyll-corpuscles which are morpho- 

 logically the same as the starch-forming corpuscles 

 and can be replaced by them are also able to 

 form starch-grains from sugar, as proved by the 

 experiments of Boehm, Acton, Meyer, Laurent, 



