130 Arlow Burdette Stout 



Schwarz (1892) describes and figures "Chromatinkugeln" in certain 

 resting nuclei of Vicia faba, Lupinus luteus and Hyacinthus orientalis. 

 Later in the same year Rosen (1892) distinguishes in vegetative nuclei 

 of Scilla sibirica two kinds of "Kernkorperchen", the "Eunucleolen" 

 and the "Pseudonucleolen". He shows that the substance of the latter 

 is the same as that of the chromatin. 



Zacharias (1895) describes "Nebennucleolen" or "Pseudonucleolen" 

 in Cucurbita Pepo. He even observed these bodies in the nuclei of living 

 hair cells. He states that they are chiefly distributed about the peri- 

 phery of the nucleus and that they stain blue or violet with "Jodgrun 

 und Diamantfuchsin" while the nucleoles stain red. He concludes that 

 these bodies are "Nucleinkorper". 



Rosenberg (1904), was the first to discover that in Capsella, Zostera, 

 and Calendula the number of these bodies is the same as that of the long 

 known chromosomes of the division figures; that is the chromosomes 

 are in reality represented in the resting nuclei by definite chromatic 

 masses, the "pseudo-nucleoles , '. Overton (1905) proposed the term 

 "prochromosomes" for the similar chromatin bodies which he found 

 in the resting nuclei of the somatic cells of Thalictrum purpurascens and 

 Calycanthus floridus, and which, as he points out, are not only too large 

 to be considered as mere knots of the reticulum, but are of the same 

 number as the chromosomes. He finds that each chromosome is repre- 

 sented by a definite center of chromatin material, the prochromosome, 

 which enlarges directly into the chromosome of the prophases. These 

 are usually much smaller than the chromosomes of the division stages 

 and their shape may or may not be quite similar. The presence of pro- 

 chromosomes in resting nuclei has since been reported by many investi- 

 gators. Miyake (1905) for Galtonia candicans, Yamanouchi (1906) for 

 Polysiphonia violacea, and Rosenberg (1907) for Hieracium Auricula and 

 H. venosum. Laibach (1907) repeated Rosenberg's studies on Capsella 

 and verified the observations regarding prochromosomes; he also found 

 that prochromosomes are present in a number of other Cruciferae. Davis 

 finds prochromosomes in Oenothera grandiflora (1909) and in Oenothera 

 biennis (1910). Lundegard (1909) adds to the above list of plants pos- 

 sessing prochromosomes the species Calendula officinalis, Achillea Mille- 

 folium, Anthemis tinctoria and Matricaria Chamomilla, In his paper of 

 1909 Overton gives a full review of the literature bearing on the theory 

 of the individuality of the chromosomes. Later in the same year Rosen- 

 berg (1909 b) reported the presence of prochromosomes in forty species 

 of plants, and many still more recent investigators have made similar 



