Further Studies on the Apogamy and Hybridization of the Hieracia. 27^ 



between apogamy and polymorphism, and the question probably con- 

 nected herewith, the origin of the apogamy. 



Strasburger is the first who has raised this problem parti- 

 cularly. In his interesting paper on the apogamy in Alcliiiiiilla (1904), 

 he has rather extensively treated the question of the relation of 

 apogamy to polymorphism. By examination of some Rubi and Rosae 

 he has shown that they were normally sexual, so that we dare not 

 speak of an absolute connection between the two phenomena. Still, 

 he supposes that in the polymorphic Eualcliimillae "übermässige Mu- 

 tation" has caused the sexual abnormality which here also becomes 

 apparent b}" the degeneration of the pollen. His opinion is the 

 following (1. c, p. 152): "Wenn aber übermäßige Mutation die Sterilität 

 fördern sollte, so würde sie das Fortbe'^tehen der betroffenen Art ge- 

 fährden. Apogame Fortpflanzung stellt sich als Aushilfe in bestimmten 

 Fällen ein, doch auch sie dürfte Rettung wohl nur für eine phylo- 

 genetisch begrenzte Zeitdauer bringen, da die apogame Art aller der 

 Vorteile verlustig geht, welche die gesclilechtliche Fortpflanzung mit 

 sich bringt". In his summary (p. 160) he repeats the same opinion. 

 It seems then that he thinks the commencement of the period of mu- 

 tation to be prior to the apogamy and the latter called forth by 

 excess of the mutation. In Eualcliimilla he supposes that the mutation 

 period is over, while about Hieracium he says (p. 137): "An sich er- 

 scheint die Möglichkeit der Fortdauer der Mutation bei Hieracien 

 nicht ausgeschlossen. Denn es ist durchaus nicht bewiesen, daß diese 

 mit Eintritt des Geschlechtsverlustes ihr Ende nehmen müsse", and 

 here he refers to the polymorphic alga genus Caulerpa, in which no 

 sexual propogation has been found, and to the inheritable bud-mutation 

 found by R. v. Wettstein (1904) in Sedwn reflexiun. In my opinion 

 the investigations on the Hieracia are rather to be interpreted in the 

 following way. The presence of apogamy fixes the new mutants, 

 which in a normally sexual genus would perhaps disappear by crossing 

 with the parent species; but mutation (polymorphism) and apogamy 

 cannot be considered as cause and effect. 



After Strasburger another German botanist G. Tischler has 

 taken up the question in his cytological studies on hybrids (1908), 

 taking a special interest in the slight production of pollen, so frequent 

 in many polymorphic genera, a fact which he connects with the 

 apogamy. He says (1. c, p.138): "Es erscheint wohl dab^i sicher, 

 diß nicht die Apogamie das Primäre, die Pollenreduktion das Sekun- 

 däre ist, sondern daß gerade umgekehrt erstere sich einfand, nachdem 



liid'jktivc Absummungs und Vererbuni;s]t:lire. IM. 1'"^ 



