232 VEGETABLE PHYSIOLOGY 



than mere specks, make their appearance, while the highest 

 powers of the microscope fail to enable an observer to 

 detect the presence of any form of plastid before or during 

 the deposition. Instead, the minute granules can be seen 

 to arise in a homogeneous transparent hyaline protoplasm. 

 The same phenomenon occurs in connection with the 

 deposition of starch grains in the cells of young developing 

 embryos, in the early stages of the formation of the seed. 

 The protoplasm of the cells may be seen to have the form 

 of a coarse network with many small meshes, which are 

 empty spaces or contain only cell- sap. There is no leuco- 

 plast inside them, nor anything comparable to one. The 

 starch grains originate in these meshes at some point in 

 contact with the protoplasm and gradually increase in size 

 till they fill them. In some cases simple, in others com- 

 pound, grains of starch are thus developed. 



In a large number of the Fungi which store up carbo- 

 hydrate reserve materials, these take the form of glycogen. 

 This is a substance which presents a somewhat close 

 resemblance to starch, being readily converted into sugar 

 in a manner almost, if not quite, identical with that 

 which is characteristic of starch. It is coloured brown by 

 iodine. It is usually deposited in amorphous form in the 

 interior of the fungal hyphse, or of particular cells of them. 

 In a few cases there are definite granules, which to a 

 certain extent resemble grains of starch, and which have 

 been stated to originate in certain corpuscular bodies 

 resembling leucoplasts. In most cases the deposition 

 appears to be effected by the protoplasm. 



Another carbohydrate which shows a certain resem- 

 blance to starch, though perhaps not a very close one, is 

 inulin. The distribution of this material is much more 

 limited than that of starch, but it is known to occur in 

 several groups of plants, being conspicuous in many of the 

 Composite among the Dicotyledons, and in several species 

 of the LiliacecB, Amaryllidace<z, and other allied orders 

 among the Monocotyledons. Like starch and glycogen, it 



