MEIOSIS IN DIGITALIS FERRUGINEA WITH SPECIAL REFERENCE TO THE ANACHROMATIC AND CATACHROMATIC PROCESSES

Abstract

Denniston (I9I3) reported an investigation of the mitotic process in Gentiana procera. His results showed that the chromosomes of this species are very small and that they retain their visible individuality for a much longer period than larger chromosomes do. The prophase was the only stage in which the chromosome's individuality was said to be lost. Eichhorn (I930) also worked with the mitotic process of small chromosomes, using for his material several species of squash. During the entire process the individual chromosomes remain visible, but Eichhorn speaks of the prophase bodies as prochromosomes and not true chromosomes. Yasui (I9iI), who studied the life history of Salvinia natans, saw nothing unusual in the behavior of the chromosomes in the microsporocytes. De Litardiere (I92I), several years later, also worked with Salvinia. natans and Azolla caroliniana. According to this author, the chromosomes in these species are extremely small, ranginog from 0.5 to I.5 microns in length. He noticed that those species of ferns with extremelv small chromosomes exhibited a very different method of behavior in the telophasic, interphasic, and prophasic stages. Since the apparent structure and size of the chromosome of Digitalis fcrruginea are similar to those of A2zolla caroliniana, Salvinia auriculata, and S. natans, I attempted to determine whether or not there was a similarity in the chromosome behavior of Digitalis ferruginea. and the two genera of water ferns mentioned, Azolla and Salzvinia. It must be noted that de Litardiere's (I92I) study was made of somatic mitosis, while this study has been concerned solely with the meiotic divisions. During the months of June, July, and August of the year I93I, flower buds of Digitalis ferruginea were gathered. In order to be certain that material in the critical stages was secured, Belling's iron-aceto-carmine smear method was used to identify the various maturation stages. One anther from each bud was used to check the stages; the three remaining anthers in each bud, two usually older or younger than the anther used, were then