GuilHermond - Atkinson — 112 — Cytoplasm 



Considering this from a different angle, one of our students, 

 Gautheret, has shown that the production of chlorophyll may be 

 experimentally obtained in most roots when they are grown under 

 certain conditions (in the presence of light and in media contain- 

 ing a certain quantity of sugar). Thus, for example, in the root 

 of the barley, whose cells normally contain a chondriome composed 

 of a mixture of chondrioconts, rods and mitochondria, in which 

 plastids and genuine chondriosomes are indistinguishable, Gau- 

 theret has succeeded in obtaining large chloroplasts, entirely com- 

 parable to those encountered in the leaves of the same plant, by a 

 differentiation of some of these elements. 



The series of investigations undertaken with the aid of mito- 

 chondrial methods, either by us in the phanerogams or in our 

 laboratory by Emberger and Mangenot on the pteridophjrtes and 

 algae, have permitted us definitively to solve this problem which 

 has remained obscure for so long, namely, the origin and life his- 

 tory of chlorophyll-containing plastids. The progress made since 

 the work of Schimper and Meyer may be judged by comparing the 

 state of this question when there were no methods for preserving 

 plastids in stained preparation and when the investigator had to 

 be content with incomplete observations of living material, to the 

 present status of the question with its very accurate data obtained 

 by mitochondrial technique, completed by observation of living 

 material. 



It is now evident that the chlorophyll-containing plants possess 

 two categories of organelles which are permanently found in every 

 cell, both of which show all the characteristics of chondriosomes 

 in animal cells. 



The first category, whose role it has not been possible to define 

 completely, corresponds to the chondriosomes found in cells of 

 animals and fungi. Its elements may be called inactive chondrio- 

 somes or even genuine chondriosomes. 



The second category, peculiar to chlorophyll-containing plants, 

 corresponds to the plastids of Schimper. These are to be dis- 

 tinguished under the name plastids. 



These two categories of organelles seem each to keep their 

 individuality in the course of cellular development and seem to 

 form only by division of pre-existing elements. This behavior, 

 difficult to demonstrate for the plastids in the cells of phanero- 

 gams, is absolutely proved by what is known regarding the chloro- 

 plasts of green algae, by the study of Anthoceros, and especially, 

 by the observations of Emberger on Selaginella. It is extremely 

 probable, also, that these characteristics are shared by the genuine 

 chondriosomes, since these elements are present in all cells, since 

 they have never been observed to form de novo or to disappear 

 and since they are capable of division. Indirect arguments in 

 favor of this opinion may be drawn, moreover, from the behavior 

 of the plastids which are very similar to them. 



The two categories of elements have (except in many algae 

 in which chlorophyll persists in all stages), the same characteris- 



