Biologie. — Morphologie, Befruchtung, etc. — Algae. 627 



marsh is regarded as a separate formation. As important character- 

 forms among the freshwater Algae tor characterising thc aquatic 

 formations the Cladophovaceae , Vauchevia and the Conjervales, the 

 Coujugatae , Oedogonium etc. may be mentioned. A large number of 

 minor groupings will have to be distinguishcd as associations. In 

 addition to these there are more intimate relations between certain 

 forms, producing what is termed a consortium {e. g. Cladophoraceae 

 Avith their growth of characteristic epiphytes, the organisms included 

 within an algal tangle etc.). Periodicity in aquatic Vegetation is of 

 two kinds — seasonal or irregulär — , and depends on factors of two 

 kinds. The seasonal factors are direct (e. g. changes in light-intensity 

 and temperature) or indirect (e. g. seasonal change in dissolved oxygen 

 owing to seasonal changes of temperature of water), and are the 

 determinants of the regulär periodicity offen observable. The latter 

 is interfered with by the irregulär factors (e. g. varying periods of 

 maximum and minimum temperature, occasional spells of drought 

 etc.). We have also to distinguish correlated factors, which represent 

 the influence of the constituents of the Vegetation in a piece of water 

 upon one another. and which may be seasonal or irregulär. The 

 inherent tendenc}^ of the plant has also to be considered. For ecolo- 

 gical purposes we still require to kno^v the determining factors (geol. 

 formation, altitude, ehem. composition of water etc.). A Single pond 

 is taken as an example of the method of Observation, and of the 

 kind of results to be obtained. F. E. Fritsch. 



Hill, T. G. and E. de Fraine. On the Seedling Structure of 

 Gymnosperms. (Annais of Botany. Vol. XX. p. 471—473. 1906.) 



The Gymnosperms as a whole conform to Van Tieghem's type 

 3 of rotation; the phloem groups brauch to right and left of the 

 xylem groups within, the protoxylem becomes external and the 

 phloem groups fuse. There are three varieties of this type but these 

 three merge into one another: 1) the cot3dedonary bündle is endarch 

 throughout and the rotation of the protoxylem is very indefinite; 

 e. g. Cephalotaxus and Taxus; 2) the seed-leaf-trace is endarch but the 

 rotation of the proxylem takes place in the hypocotyl, e. g. Cedrus; 

 3j the rotation of the xylem and the bifurcation of the phloem take 

 place in the seed-leai, e. g. Pünis.- The cotyledonary bundles of 

 Cephalotaxus and Taxus exhibit a mesarch structure. The authors 

 conclude that the numerous cotyledons occuring in many plants 

 have been formed by the Splitting of preexisting ones. • 



M. Wilson (Glasgow). 



Foslle, M. and M. A. Howe. Two new coralline algae from 

 Culebra, Porto Rico. [Bulletin of the Torrey Botanical Club. 

 XXXIII. p. 577—580. plates 23—26. Text-figures 1 and 2. November 

 [December 19.] 1906.) 



Includes descriptions and illustrations of two new species of 

 coralline algae, GonioUthon acropetum. Foslie and Howe and Litho- 

 phyllum Antillanan Foslie and Howe, both from the island of 

 Celubra lying between St. Thomas and Porto Rico proper. Both 

 species are figured at natural size, details of structure being shown 

 by photomicrographs and text-figures, and the relationship of the 

 two is fully discussed. IMaxon. 



