194 Biologie. — Varietäten, Descendenz, Hybriden. 



Kanngiesser, F., Beitrag zur Kenntnis der Lebensdauer 

 arktischer Sträucher. (Ber. Schweiz, bot. Ges. XXI. p. 188 — 

 199. 1912.) 



Untersuchung von Material aus Maalselodalen (Tromsö). 

 Es wurden untersucht: Salix polaris, herbacea, Phyllodoce coendea, 

 Asalea procumbens, Dryas, Empetrian , Betiila nana, Salix reticulata, 

 Arctostaphylos bezüglich des stärksten Durchmessers (Dm) das 

 Stämmchens bezw. des Holzkörpers, des stärksten Wachstumsradius 

 (WR) desselben, dann die aus WR und Anzahl der Ringe be- 

 rechnete mittlere Jahrringbreite (MR). Ein Beispiel: 



Arctostaphylos alpina, Dm =^6,6; WR = 4; MR0,10; Alter 39 

 Jahre. Matouschek (Wien). 



Bartlett, H. H., Mutation en masse. (American Naturalist. IL. 

 p. 129-139. 1915.) 



The writer's experiments with Oenothera-species led him to the 

 discovery of certain strains that gave rise by mutation to large 

 numbers of dwarfs. The present paper publishes a preUminary 

 report of this phenomenon in Oenothera Reynoldsii, a new species 

 coUected by E. J. Reynolds at Knoxville, Tennessee. In the 

 small Fj and F.^ cultures (10 and 5 plants in number) no diversity 

 was found, but the Fg-generation (26 plants) exhibited a segregation 

 into three marked types: the parental form, forma typica, and two 

 dwarf types mut. semialta and mut. debilis. 



About these mutations the writer gives as capitulating: 



1. The individuals of forma typica are of two kinds, (a) those 

 which do not throw dwarfs and {b) those which throw from 60 per 

 cent, to 80 per cent, of dwarfs. 



2. The dwarfs are of two kinds, one of which, mut. semialta, 

 is intermediate between f. typica and the extreme dwarf, mut. 

 debilis. 



3. Mut. semialta reproduces itself in the greater parts of its 

 progeny, but throws a small number (seemingly about 7 per cent.) 

 of mut. debilis. 



4. Mut. debilis does not throw either f. typica or f. semialta. It 

 comes true, except for the fact that it rarely throws mut. bilonga. 



This mut. bilonga is by far the most interesting of the variants 

 of Oenothera Reynoldsii. It shows, though thrown by mut. debilis, 

 a. return to the stature of mut. semialta. It is characterized by the 

 longest fruits in the subgenus Onagra. This phenomenon, called by 

 the writer mutation en masse, bears a certain degree of resem- 

 blance to Mendelian segregation. The fundamental mutation which 

 causes the diversity possibly occurs in only one of the two gametes, 

 in a generation preceding the one in which diversity becomes mani- 

 fest. The most interesting problem seems to be the origin of mut. 

 bilonga, involving, as now seems probable, the origin of a new 

 character. M. J. Sirks (Bunnik). 



Cockerell, T. D. A., Specific and varietal characters in 

 annual sunflowers. (American Naturalist. IL. p. 609—622. 1915.) 



Excluding from the group Helianthus annuus the species H. 

 bolanderi Gray, H. exilis Gray, H. floridanus Gray and H. tephrodes 

 Gray, there remains the subgenus Helianthus s. str. or Euhelianthus , 

 containing 1. H. Annuus L., based on the large cultivated form H. 

 macrocarpus DG,, 2. H. lenticularis Douglas, 3. H. aridus Rydberg, 



