PROTOCOCCUS PLUVIALIS. 527 



The contents of cells which have been long dried, 

 generally assume an oily appearance. The oily material, 

 then resembles in every respect the red globules which 

 have been described as being oil, in various species of 

 Cltroolepus, such as C. oleiferum, hercynicum, velutinum, 

 aureum, and Jolithus. Like the latter, also, it is capable 

 of becoming green. 



The change of colour from green to red in Euglena 

 appears to be a process very nearly allied to that which 

 takes place in Protococcus, if it be not identical with it. 

 Great confusion and much contradiction is evident in 

 nearly all writers who have referred to the subject of the 

 colouring matter in plants, and accurate researches on 

 the subject would appear to be of the greatest moment. 



The red substance of Prot. pluvialis is not always of 

 an oily aspect ; it only becomes so in more advanced age. 

 Whether it really be oil, the author does not venture to 

 decide, although the relation of the material towards 

 light, alcohol, and ether (and he might have added, 

 water), are in favour of its being oil. And according to his 

 researches, oil is much more generally distributed than 

 has been supposed, among the lower Algae ; occurring in 

 many true brown spores, such as of (Edogonium, 

 Spirogyra, Vauclieria, &c. 



When still or motile cells are brought in contact with 

 a very weak watery solution of iodine, they become 

 internally, in most parts, of an intense violet or blue colour. 

 The author, however, does not believe that this colour 

 actually, in all cases, depends upon starch, as in the 

 present state of chemistry it would appear necessary to 

 conclude that it did. He was satisfied that the red sub- 

 stance was invariably and entirely coloured blue. When 

 some of the cells were ruptured, all the previously red 

 globules had become entirely dark blue, so that the red 

 colour was wholly removed, whilst the green substance of 

 the cell with its granules was not so much altered, though 

 also bluish. The larger drops also appeared blue, so 

 that there was no difference whatever, in this respect, 



