- Project Runeberg -  The Swedish Nation in Word and Picture /
109

(1921) [MARC] Author: Herman Lundborg
Table of Contents / Innehåll | << Previous | Next >>
  Project Runeberg | Catalog | Recent Changes | Donate | Comments? |   

Full resolution (JPEG) - On this page / på denna sida - Part I - Professor Otto Rosenberg, Stockholm, Genetic Cytology in Sweden

scanned image

<< prev. page << föreg. sida <<     >> nästa sida >> next page >>


Below is the raw OCR text from the above scanned image. Do you see an error? Proofread the page now!
Här nedan syns maskintolkade texten från faksimilbilden ovan. Ser du något fel? Korrekturläs sidan nu!

This page has never been proofread. / Denna sida har aldrig korrekturlästs.

:

GENETIC C YTOLOGY IN SWEDEN

BY

Professor OTTO ROSENBERG

STOCKHOLM

The tendency of cytological investigation which

aims at a connection with genetics has, in Sweden, chiefly followed two
lines: on the one hand, an examination of parthenogenesis, its nature and
causes; on the other, the study of bastard forms, in order, by an examination of
the chromosome conditions in the germ«cells, to obtain a clearer idea of the nature
of hybridizing.

As far as the first question is concerned, Juel’s important work on partheno«
genesis in Antennaria alpina (1900) must be considered as being of fundamental
importance. His discovery that, in the embryo«sac and eggformation in the case
of this plant, the reduction«division is entirely absent so that, from the very be«
ginning, the egg has the somatic chromosome number, has later on been confirmed
in numerous cases; by Murbeck’s investigation (1901) with respect to the poly«
morphic genus Alchemilla, and by examinations of Taraxacum (Juel 1905), Hier«
acium (Murbeck 1904; Rosenberg 1907) and of Eupatorium (Holmgren 1919).

The apomictical or parthenogenetical development in the genus Hieracium
proved to be of special interest. Ostenfeld, by means of castration experiments,
had already shown that seed«formation without fertilization occurs in most species
of this genus. The present writer showed, later on, that the embryo«sac in the sub«
genus Archieracium was formed according to the Hnfennan’a=scheme, while, in the
case of the sub«genus Pilosella, a vegetative cell in the neighbourhood of the sexual
embryo«sac grows out to an aposporous embryo«sac and displaces the sexual one.

Already in Juel’s Antennaria=work, the supposition is put forward, that par«
thenogenesis is connected, in one way or another, with a previously existing bas«
tardizing process, an opinion which has, later on, been developed by Ernst into
an hypothesis of bastardizing as the cause of apogamy.

Holmgren and the present writer also come to a similar conclusion, as the
result of a cytological investigation of apomictic Hieracium= and Eupatorium=
forms, where triploid chromosome numbers are specially characteristic.

In respect to the cytological investigations of bastard forms, our interest is
chiefly attracted by the problem of the chromosome«conditions in the formation of
germ«cells or, more definitely, in regard to the heterotypic division.

In 1904, the writer found in the genus Drosera a species«bastard which, in
cytological respects, presented features of no slight interest; especially, because the
germ«cells of the parent plants showed different chromosome«numbers the one 10 the
other 20. The bastard itself showed, as was to be expected, 30 chromosomes in
the somatic cells. But how does this chromosome arrangement agree with the
heterotypic division? Juel had previously shown that, in a 5yringa«bastard during
metaphasis of the heterotypic division, there took place an extremely irregular chro«
mosome«distribution, which results in sterile germ«cells. In the case of the above«

<< prev. page << föreg. sida <<     >> nästa sida >> next page >>


Project Runeberg, Tue Dec 12 01:37:45 2023 (aronsson) (download) << Previous Next >>
https://runeberg.org/swednation/0135.html

Valid HTML 4.0! All our files are DRM-free