530 SUMMARY OF CUKRENT RESEARCHES RELATING TO 



BOTANY. 



GENERAL, 



Including the Anatomy and Physiology of Seed Plants. 



Cytology, 

 Including: Cell-contents. 



Chondriosomes in Plant-cells.* — G. Lewitsky has studied choudrio- 

 somes as seen in living and in fixed cells of Elodea canadensis, and finds 

 that fixing media, by destroying the living plasma and tlie embedded 

 structures (including the chondriosomes), give the peculiar net like 

 appearance to fixed cells. It is now possible to photograph the living 

 cell and its contents, and the chondriosomes are found to 1)6 quite 

 different from those depicted for fixed cells. The cytoplasm of living 

 meristematic cells consists of a fluid apparently homogeneous plasma in 

 which are embedded more solid bodies in the form of isolated threads, 

 small rods, granular threads and granules, which on the one hand possess 

 the characters of the chondriosomes of animal cells, and on the other 

 hand correspond to the threads described by Flemming upon which he 

 bases his " Filar Theory." 



Chloroplast-forniation.t — G. Lewitsky has also studied the forma- 

 tion of chloroplasts in Elodea canadensis, and finds that the ordinary 

 fixing mediums completely destroy the products of the early stages of 

 such formations. By photographic reproduction of the living cells the 

 author finds that the chloroplasts arise in the form of green " chondrio- 

 conts," i.e. small rods or threads, embedded in the cytoplasm. These 

 structures swell at the ends and become dumb bell-shaped ; finally the 

 swollen portions are detached from one another and develop into young 

 chloroplasts of the usual oval shape. 



Origin of Chloroplasts.J — A. Forenbacher has studied the develop- 

 ment of chloroplasts in Tradescantia vin/inica in order to test the theories 

 of those investigators who claim that these bodies are derived from 

 chondriosomes. A careful examination was made of the older parts of 

 the stem and leaf, where the green chloroplasts are fully developed, up 

 to the dermatogen-layers of the stem-apex where they have their origin. 

 Tlie chondriosome theory was fully confirmed, for all stages of transition 

 between the chondriosome and the chloroplast were found. The young 

 chloroplasts of the upper cortex are fully developed, but in the layers 

 nearer the dermatogen they are rudimentary and their structure is merely 



* Ber. Deutscb. Bot. Gesell., xxix. (1912) pp. 685-96 (1 pi.). 

 t Ber. Deutsch. Bot. GeseU., xxix. (1912) pp. 697-703 (1 pL). 

 X Ber. Deutsch. Bot. Gesell., xxix. (1912) pp. 648-60 (1 pi.). 



