1 84 ROBERT H. BOWEN. 



osition of starch in the plastid primordia has now been traced, 

 especially in cells of the root-cap and periblem, and their trans- 

 formation into typical plastids is undoubted. My results thus 

 confirm the morphological results obtained by Guilliermond, who 

 has particularly emphasized as characteristic the generally 

 elongate shape of the proplastids in all sorts of meristems. 



The plastidome is characterized further by its general tendency 

 to be oriented in a specific way with respect to the spindle of a 

 dividing cell. The facts have been brought out particularly by 

 Nassonov ('18), and my results corroborate his account, and 

 push the matter somewhat further. In Fig. 2, an especially 

 fine prophase example of the orientation of the proplastids with 

 respect to the future spindle is shown. It now seems more and 

 more probable that this behavior of the plastidome in cell 

 division is a very common phenomenon in plant cell-division, 

 and has been long overlooked simply because of the technical 

 difficulties which so often bring disaster at the particularly im- 

 portant moments of division. 



Guilliermond has claimed that the plastidome is a specially 

 differentiated part of the chondriome, characteristic of plant 

 cells. My observations on root-tip cells do not offer any evidence 

 in support of such an identification. Certainly these bodies 

 offer distinct differences in staining capacity as compared to 

 any other cellular elements in plants, and it does not seem 

 possible to settle their status on the basis of their behavior in 

 root-tips. 



The Pseudochondriome. This comprises a group of bodies to 

 which Guilliermond has given the name of "inactive chondriome," 

 in contrast to his "active chondriome " or plastidome. There are 

 in fact several good reasons for believing that these bodies 

 are equivalent to the chondriosomes of animal cells, but pending 

 more complete evidence I have chosen to use the term pseudo- 

 chondriome as descriptive of their similarity to chondriosomes, 

 but without committing myself for the present to any definite 

 view of their real nature. In my first reports these bodies 

 were confused with the osmiophilic platelets, because of certain 

 morphological similarities when representatives of the two 

 classes are viewed in the proper plane. Indeed, several people 



