Guilliermond - Atkinson — 218 — Cytoplasm 



There has been attributed to chondriosomes in animal cells a 

 preponderant and direct role in the elaboration of metabolic prod- 

 ucts : fats, granules resulting from all sorts of secretion, pigments. 

 According to this conception the chondriosomes have a role rather 

 analogous to that of plastids in chlorophyll-containing plants. 

 This conception seemed, for a while, all the better established since 

 the later research in plant cytology shows that the plastids of the 

 phanerogams have exactly the same morphological and histochem- 

 ical characteristics as the chondriosomes. Further research did 

 not, however, confirm this role, at least, in most cases, and if it 

 exists, it is very limited. The role of the chondriosomes is still 

 unknown. Nevertheless the fact that they are closely related to 

 the plastids of chlorophyll-containing plants permits us to imagine 

 that the chondriosomes have a very important function in cellular 

 metabolism. 



The plastids:- The cells of chlorophyll-containing plants are 

 distinguished from the cells of animals and fungi by the presence 

 of a second category of organelles, the plastids. It is definitively 

 proved that these are organelles which form only by division of 

 pre-existing plastids and which maintain their individuality in the 

 course of development. In those higher plants in which chlorophyll 

 is not continuously elaborated, the plastids which are functionally 

 inactive have the same forms and the same histochemical charac- 

 teristics as the chondriosomes, among which they can not be identi- 

 fied in embryonic cells. Forming with them a chondriome of homo- 

 geneous appearance, the plastids are distinguishable only by their 

 power, during cellular differentiation, of elaborating or accumulat- 

 ing chlorophyll, carotinoid pigments and starch, and by the fact 

 that the products which they engender modify their shapes. This 

 modification is only transitory in the case of starch. The starch 

 grain formed within the plastid is hydrolyzed in the interior of 

 the plastid which then recovers its inactive shape until such time 

 as there is a new elaboration of starch. Depending upon the case 

 in question, the plastid is transitory or permanent. During the 

 production of chlorophyll, the plastid, in filling up with pigment, 

 hypertrophies and appears as a large spherical body. It may re- 

 main indefinitely in this state or, in some cases, it may lose its 

 chlorophyll and appear again as a minute chondriosome. Plants 

 exist, many algae and bryophytes for example, in which chloro- 

 phyll is permanently secreted and in which all the cells, at the 

 same time, contain both large highly differentiated chloroplasts 

 and small chondriosomes, both transmitted by division from cell 

 to cell. The existence of such groups furnishes proof that, in the 

 higher plants, the chondriosomes capable of elaborating starch, or 

 of accumulating chlorophyll, do not have genetic relationships 

 with those lacking this function. There exists in embryonic 

 cells of Selaginella a single chloroplast, shaped like a chon- 

 driocont and differing from the other chondriosomes by its slightly 

 larger size. This, together with Anthoceros which has a single but 



