Cytologie und Befruchtung. 267 



cineses de maturation dans de nombreuses ovogenfeses 

 (Pristlurus, Scillium, Trigla, Gasierosteus, Amphloxiis, Ciona). 

 La derniere cinese ovogoniale est suivie d'un repos nucleaire. 

 Le noyau ovocytaire passe d'abord par un stade de synapsis pen- 

 dant lequel se forme aux depens de filaments minces, un spireme 

 epais. Celui-ci se dlvise longitudinalement. Puis les chromo- 

 somes, toujoLirs constitiies de leurs branches, subissent une 

 Sorte d'expansion de leur substance. II se forme un reseau 

 qui remplit tout le noyau. Les chromosomes peuvent y devenir 

 plus ou moins indistincts. Neanmoins, l'auteur les suit durant 

 tout le developpement de l'ovocyte. 



L'auteur retrouve donc, lors du premier developpement de 

 l'oeuf, des avant la periode d'accroissement, la serie de pheno- 

 menes qui caracterisent le debut des cineses de maturation dans 

 la sporogenese vegetale et dans la Spermatogenese animale. 

 De plus, Marechal a observe, durant le synapsis, des indices 

 tres clairs d'un accolement, deux par deux, des filaments 

 chromosomiques minces, et il interprete le „dedoublement longi- 

 tudinal" du spireme epais comme la reapparition de ces fila- 

 ments conjugues. V. Gregoire. 



POND, R. H., TheBiological Relation of Aquatic Plauts 

 to the SubStratum. (U. S. Fish. Comm. Report for 1903. 

 1905. p. 483—526. fig. 1—6.) 



The following plants were mainly experimented with, 

 Vallisneria splvalis, Raminculiis aqiiatllis trichophyllus, Elodca 

 canadensis, Myviophylliim spicatum, Potamogeton obtiisifolius, 

 and P. perfoliatns. The most important facts established 

 regarding these are: that they are dependant upon rooting in 

 their substratum for optimum growth ; that their roots function 

 for absorption as well as for attachment; that there is an 

 upward current in these plants from roots to stems and leaves; 

 that the presence of root hairs is the rule rather than the 

 exception. The retardation of growth of unattached plants is 

 not due to Imbibition of photosynthesis, but rather to a patho- 

 logical accumuiation of starch, which eventually results in death. 

 The primary cause for this appears to be the inability of the 

 plants deprived of their substratum, to obtain enough phos- 

 phorus and potassium and as well, possibly, of other elements. 

 Concludes that these plants are terrestrial forms, adapted to 

 aquatic habit, rather than descendants of any primitive, com- 

 paratively undifferentiated water-living form. 



Ceratophyllum which produces no roots, is able to absorb 

 the necessary amount of mineral salts from the water in which 

 it merely floats. H. M. Richards (New York). 



Stevens, F. L., Oogenesis and Fertilization in Albiigo 

 Ipomeae-panduranae. (Bot. Gazette. XXXVIII. 1904. p. 300 

 —302.) 



