Morphologie, Teratologie, Befruchtung, Cytologie. 451 



of both the heterotype and homotype divisions were also studied 

 in the case of Crepis virens: the latter species was used, in addition, 

 in the study of the somatic divisions. 



The most important of the results obtained are the following: 



During the period just preceding synapsis the nuclei of those 

 Compositae which have been examined were found to contain a 

 more or less fine reticulum. No definite aggregations of chromatin 

 which could be regarded as pro-chromosomes were in any case 

 found upon this reticulum. The reticulum passes into the synaptic 

 contraction, during which it is gradually converted into a very long 

 delicate spirem. No chromatic aggregates were observed during 

 this stage, and no definite parallelism of the threads occurs other 

 than is inevitable in any closely coiled System of filaments. The 

 spireme which emerges from the closely wound synaptic knot has 

 become thicker, and, in favourable examples, shows a series of 

 chromatic particles (chromomeres) embedded !in a less deeply stai- 

 ned linin thread. No evidence was found of the existence of two 

 parallel spiremes. The spireme again draws itself together in the 

 "second contraction". In doing so it forms a series ofloops, radiating 

 form a common centre. The loops become detached, thicken consi- 

 derably, and pass towards the periphery of the nucleus. Here they 

 assume the shape of rings, crosses, parallel rods, twisted rods, or 

 remain as loops. The loops which are formed in this way are actualy 

 the bivalent-chromosomes of the heterotype division, and are con- 

 stituted of two univalent-chromosomes joined end to end. The 

 daughter nuclei, when formed, do not pass into a condition of 

 complete rest. 



In the somatic divisions no continuous spireme is formed, and 

 no prochromosomes are visible in the resting nuclei. 



There are two types of pollen wall in the Compositae. All the 

 Tubulißorae which have been examined possess pollen grains wilh 

 an unfolded exine, whilst the exospore of all the Liguliflorae ob- 

 served is thrown into a number of distinct folds. The details of the 

 structure of the pollen-membrane is reserved for a separate part of 

 these 'studies'. Agnes Arber (Cambridge). 



Clark, J. J., Abnormal Flowers of Amelanchier spicata. (Ann. 

 Bot. XXVI. p. 948—949. Textfig. 1912.) 



Petalody of the stamens offen occurs in the Rosaceae, but in 

 the present note the author records-.that the reverse condition has 

 been observed in two plants of the N American Amelanchier spicata, 

 Koch., growing in the Royal Botanic Gardens, Kew. Here the 

 margins of the petals were infolded, and, in the most extreme 

 cases, this infolding gave rise to a distinct anther containing pollen. 



Agnes Arber (Cambridge). 



Gates, R. R., Somatic Mitoses in Oenothera. (Ann. Bot. XXVI. 

 p. 993—1010. 1 pl. 1912.) 



The present paper records observations made upon a Single 

 plant of Oenothera lata. The author has also made a study of other 

 forms. The individual of O. lata from which this account is chiefly 

 drawn contained 15 chromosomes in its megaspore mother-cells and 

 in the cells of the nucellus. In the nucellus, however, there were 

 occasional cells containing a different number. Thus over 50 cells 



