244 Morphologie, Teratologie, Befruchtung, Cytologie. 



radius of 2—4 meters soon become covered with vigorous upright 

 shoots. 



The layering habit of Picea mariana has been mentioned in 

 literature for specimens growing under partial cultivation , but its 

 importance in increasing the stand upon rocky areas seems to have 

 excaped notice. Jongmans. 



Mapquette, W., Note concerning the discovery ofthe nu- 

 cleus. (Bot. Gazette. LI. p. 461—463. 1911.) 



Historical reviews generally refer the discovery of the nucleus 

 to Robert Brown, perhaps adding that before Brown's work the 

 nucleus had occasionally been figured, but that the authors attached 

 so little importance to the structure that usually it is not even 

 mentioned in the text. 



The present writer fixes the attention at a quite forgotten paper 

 by F. J. F. Meyen, puplished in Linnaea, Vol. 2, 1827, p. 428, in 

 which an account is given of the nucleus of Spirogyra^ which for 

 accuracy of Observation and clearness of detailed description leaves 

 little to be desired. Figures supporting the description accompany 

 the paper. 



It is a curious fact that this work of Meyen's has dropped so 

 completely out of the current of citation. Jongmans. 



Merriman, M. L., Nuclear division in Spirogxra crassa. (Bot. 

 Gazette. LVI. p. 319—330. PI. 11, 12. 1913.) 



A summary of the results obtained that differ most from others 

 published is as follows. 



A spireme originates from material derived from both nucleolus 

 and nuclear network. The materials constituting this spireme are 

 aggregations varying in appearance, in number, and in staining 

 capacities. 



These aggregations are not the chromosomes. They greatl}'' 

 exceed in number that published for chromosomes in anj'^ species 

 of Spirogyra ; although a comparative study of plates of other in- 

 vestigators indicates that these are the bodies heterofore designated 

 as chromosomes. 



The spireme in the pachyneme stage is composed of deeply 

 stained short filaments intermixed with material of a granulär na- 

 ture. There is evidence that this granulär material was derived 

 from the nucleolus, the filamentous froAi the nuclear network. 



These two materials amalgamate to form one of intensive 

 staining capacity. The amalgamated material retains the spireme 

 form. This spireme as a whole is spherical, later elongates, beco- 

 ming cjdindrical. Cross-sections of the loops reveal their tubulär 

 structure. 



This spireme does not appear to split either transversely or 

 longitudinally, but separates at various points as would a viscid 

 mass if pulled in opposite directions. Fourteen or more tubulär 

 chromosomes for each daughter nucleus result from the elongation 

 of the coils of the spireme. These are not to be considered "pseu- 

 dochromosomes". 



At this stage and subsequently chromidia are discharged into 

 the cytoplasm. It is probable that these chromidia are concerned 

 in the development of pyrenoids. 



