21 



may be assumed to be g'oiug on throiigli the activity and 

 under the influence of the rhodoplastids. Xothing definite 

 however is knoAvn concerning- the importance and function 

 of the phycoerythrin in the rhodoplastid. 



The rhodopUistids in the assimilating cells are on the 

 whole well developed and of a dark red colour. The 

 apical cells of these assimilating rows have, however, only 

 a very small rhodoplastid each. This is a general rule, 

 and it may be due to the fact that these apical cells are 

 actively growing and dividing. 



The substances built up are apparently removed very 

 rapidly to the next inner cells away from the assimilating 

 tissue. This latter, at any rate, contains no traceable 

 quantities of starch. The food substances are in fact pro- 

 bably collected by the collecting cells from the outer 

 layers, and are then passed on to the large conducting 

 cells. They are then stored or passed up or down the 

 shoot, according to the direction in which any part of the 

 plant in need of food may draw them. 



A certain faint red colour may often be detected in the 

 finely divided rhodoplastids of the collecting and of the 

 conducting cells, but it is impossible to say whether it 

 enables assimilation to be carried on. In the centre of 

 the shoot the red colour has disappeared, and in place of 

 one red rhodoplastid we get numerous very faint green 

 leucoplastids. 



Starch is found very abundantly in the collecting and 

 in the conducting cells. Both these tissues, therefore, 

 probably act as storing tissues. 



In the root organ the cells are all found to be full of 

 starch. The root is evidently a very important organ for 

 the storage of food. It is not likely that assimilation is 

 going on very actively in the root. The rhodoplastids are 

 faint in colour and very finely divided. 



