Physiologie. — Algae. 
405 
the frost affecting only the trees which had started growth. 4. Young 
growth was injured more severely than mature trees. 5. Weak 
trees were worse affected than strong ones. 6. Thin-barked trees, 
as a rule, suffered more than thick-barked ones. 7. Conifers were 
more resistant than the deciduous trees which had started seasoned 
growth. 8. Direction of wind has a direct influence on the degree 
of injury to Stands occurring on slopes ot' different aspects. 9. Within 
the zone of frost effect the injury increased proportionately as 
the elevation decreased. 10. Limber pine, which is one of the 
hardiest trees at high elevations, becomes less hardy at low eleva- 
tions. 11. Trees growing on small mounds were more severely 
injured than those growing on level land. 12. Adventitious buds 
were stimulated on scrub oak trees, causing a more variable second 
crop of leaves than on those trees where adventitious buds had been 
previously stimulated by grazing. 13. Frost increases the sprouting 
of Robinia neo-mexicana. 14. Frost kills blossoms on both deciduous 
and coniferous trees, an undoubtedly has a material effect in redu- 
cing the seed crop. H. von Schrenk. 
Levander, K. M„ Beiträge zur Kenntniss des Sees Pitkänie- 
mijärvi der Fischereiversuchsstation Evois. (Acta Soc. pro 
Fauna et Flora Fennica, XXIX. N°. 3, Helsingfors, 1906. 15 pp.) 
The botanical part of the paper is confined to the phytoplankton 
of the lake, the higher hydrophyte-Vegetation being very poor 
(absent, except in the outlets of the rivulets). 
The plankton samples have been colleeted once in each month 
during 1904. The table teils us that the number of protophytes is 
small. In summer (June—October) Astevionella gracillima, Tabellaria 
fenestrata, Rhisosolenia longiseta, Dinobryon divergens , D.bavaricum 
and Mallomonas caudcita play the main part; the Myxophycecie are 
wanting and the Chlorophyceae are very scarce. In winter (January— 
March) practically no phytoplankton is to be found. 
C. H. Ostenfeld. 
Levander, K. M., Notiz über das Winterplankton in drei 
Seen bei Knopio. (Medd. Soc. pro Fauna et Flora Fennica, XXXII, 
Helsingfors 1906, p. 93—96.) 
The author has colleeted some plankton-samples in the neigh- 
bourhood of Knopio, Finland, during the Christmas-times of 1905. 
The samples have been taken in the lakes under a medium-thick 
ice-covering. The protophytes are very few in number, both as 
regards species and individuals. The species recorded are Coelo- 
sphaerium Naegelianum , Anabaena spiroides , Aphanisomenon ßos 
aquae, Botryococcus Braunii, Synum uvella, Uroglena volvox, Eu- 
dorina elegans, Astevionella gracillima, Tabellaria fenestrata, T. floc- 
culosa. The first enumerated species was rather numerous, but the 
colonies were to some extent disorganized. C. H. Ostenfeld. 
Levander, K. M., Ueber das Plankton des Sees Humaljärvi. 
(Medd. Soc. pro Fauna et Flora Fennica, XXXII, Helsingfors 1906, 
p. 42—46.) 
Report on the plankton of the lake Humaljärvi in the neigh- 
bourhood of Helsingfors colleeted Oct. l 8t 1907. The plankton was 
very rieh and consisted mostly of protophytes, the dominant species 
