and Laboratory Methods. 2579 



Lignier, 0. Le fruit du Williunisonia x/.^:"-^- The reinvestigation of this remarkable 

 Carr. et less Bennettitales, documents nou- r -i i i iit- i i- 



veaux et notes critique. Memoires de la ^OSSll was suggested by Wieland S 

 Societe Linneenne de Xormandie, 21 : 19- researches upon Cxcadoidea, and there 

 ^ ' seems to be considerable resemblance 



between the two forms. According to the present account, the structures in 

 IVilliamsoiiia gigas which have been described as "male fiowers " are really the 

 axes of ovulate strobili from which the layer of ovules has become detached after 

 maturity. The staminate structures were probably comparable to those described 

 by Wieland for Cycadoidea inge/is. The fruit of the Bennettitales should be con- 

 sidered not as a flower but as an inflorescence. 



A diagram showing the relationships of great groups is submitted. From the 

 Protopterideae, the ancestors of the Filicales, is derived a stock which becomes 

 differentiated into two main lines, the Salisburiales and Cordaitales. At an 

 early period the Cycadales were derived from the Salisburiales and, later, the 

 Coniferales came from the same stock. From the Cordaitales at an early period 

 came the Bennettitales and, later, the Gnetales and Angiosperms. More must 

 be known of the life history of fossil forms lying between Pteridophytes and 

 Gymnosperms, and also of fossils in these two groups before a satisfactory dia- 

 gram of relationships can be constructed. c j. c. 



Rosenberg, 0. Das Verhalten der Chromoso- So little cytological work has been done 

 rnen in einer hybriden Pflanze. Ber. d. ^ j^nt hybrids that every contri- 



deutsch. Dot. Gesell. 21 : 1 10-119, pi. 7, 1903. r r j ^ 



bution excites more than ordinary 



interest. It is well known that the various species of a given genus generally 

 have the same number of chromosomes. Prof. Rosenberg has been fortunate in 

 finding a hybrid between parents which diflier from each other both in the 

 number and size of their chromosomes. The hybrid is a cross between Drosera 

 rotundifolia and D. longifolia. D. rotundifolia has 20 chromosomes in the sporo- 

 phyte, this number appearing in the stem, leaf and root. The chromosomes are 

 short and easy to count. In the pollen mother-cell the number is always 10. In 

 D. longifolia the vegetative tissues show 40 chromosomes and the pollen mother- 

 cells 20, the chromosomes being somewhat smaller than in D. rotundifolia. The 

 chromosomes were not counted in the megaspore mother cell of either species. 



The hybrid is easily recognized by external characters, but is also charac- 

 terized by its chromosomes. The mitoses are not different from those of the 

 parents except in the number of chromosomes and consequent variation in the 

 shape of the spindle. In the sporophyte 30 chromosomes — the sum of the 

 gametophyte numbers of the two parents — was counted in the root, stem and 

 leaf. In a few cases 40 chromosome's appeared in tapetal cells. In the pollen 

 mother-cells 15 chromosomes is the dominant number, but "JO often occur and 

 occasionally mother-cells with 10 are found. All three numbers have been found 

 in the same anther. The megaspore mother-cells were not investigated. 



The fact that three kinds of pollen grains are formed has its bearing upon 

 Mendelism. The relative numbers of chromosomes in the parents and hybrid 

 support the theory that the chromosome is a permanent organ of the cell. 



c. J. c. 



