Morphologie, Teratologie, Befruchtung, Cytologie. 291 



Lawson, A. A., A Stud}' in Chromosome Reduction. (Trans. 

 Roy. Soc. Edinburgh. XLVIII. 3. p. 601-627. 3 pl. 1913.) 



This paper forms one of a series of studies by Professor 

 Lawson in which he deals with the nature and meaning of the 

 reduction divisions. 



The material used in the present investigation was the anthers 

 of Smilacina, supplemented by Kniphofia and Aloe. The principal 

 conclusions reached maj'^ be briefl)^ summarised as foUows: 



There is no evidence to show that the chromatin in the plants 

 studied ever consists of one continuous spireme. Each spireme thread 

 Shows a longitudinal fission at a very early stage. The so-called 

 synaptic "contraction" really represents a growth period. Reduction 

 is accompHshed by the temporary lateral pairing of somatic chro- 

 raosomes. The nuclear membrane does not disappear but ultimately 

 becomes closely applied to each bivalent chromosome. As this pro- 

 cess takes place the cytoplasm immediately surrounding the nucleus 

 becomes drawn out into a series of tine threads or fibrils. These 

 fibrils, which later constitute the achromatic figure, thus originale 

 directly from the cytoplasmic reticulum and merel}' represent lines 

 of tension. The achromatic figure can thus take no active part in 

 the movements of the chromosomes. 



An exceptionally high State of nutrition prevails throughout the 

 two meiotic divisions, — the cells themselves bemg temporary storage 

 Organs The very exceptional nutritive conditions. result in an acce- 

 lerated form of meristematic activity. It is suggested that the first 

 meiotic division represents two ordinary vegetative divisions which 

 have become telescoped into one. Agnes Arber (Cambridge). 



Stevens, N. E., Observations on Heterostylous Plants. 

 (Botanical Gazette. LIII. p. 277—308. pls. 21—23. 1912.) 



This paper was suggested by the "sex chromosome" described 

 in various aninials and searched for in plants. The heterostylous 

 Fagopyrum esciilentum and Houstonia caerulea were studied , prin- 

 cipal attention being given to the mitoses in the pollen mother cells. 



In Fagopyrum, in the pollen mother cell, the chromosomes of 

 the shortstyled form have nearly twice as great a diameter as 

 ihose of the long-styled form, and there is some difference in the 

 arrangement. 



In Houstonia the chromosomes of the short-styled form are also 

 somewhat larger than those of the long styled form. 



Charles J. Chamberlain (Chicago). 



Warming, E., Observations surlavaleursystemati- 

 que de l'ovule (Mindeskrift for Japetus Steenstrup. XXIV. 4°. 

 p. 1—45. 24 figs. dans la texte. 1913.) 



L'auteur traite les questions suivants concernant les differences 

 des ovules: 



1) Formation du sac embryonnaire, 



2) Types principaux d'ovules, 



3) La Position de l'ovule dans l'ovaire. Ici, l'auteur fait obser- 

 ver que les termes apotrope, epitrope, et heterotrope crees par 

 Agardh ne sont pas toujours employes correctement, la confusion 

 existant meme dans des manuels modernes. 



