Morphologie, Teratologie, Befruchtung, Cytologie. 451 



substance becomes completely dispersed over the linin-reticulum. 

 Chromatic aggregations also occur in many of the nuclei of the 

 anther tissues, notably in those of the young vascular bündle, but 

 the size and number of these aggregations are quite inconstant. 



The development of the spore wall is discussed in great detail. 

 In the mature pollen grain the wall is decorated with rodlets and 

 spines. Almost the entire growth of these rodlets and spines takes 

 place after these have become separated from direct contact with 

 the protoplast by the interpolation of the thickening bands (meso- 

 spore). Neither are they in contact with the tapetal or any other 

 cytoplasm. (The tapetal cells do not disintegrate, but are of the 

 nature of "secretion-tapeta"). The conclusion is drawn that these 

 rodlets and spines posses a certain power of growth, independent 

 of any direct protoplasmic influence, and, moreover, during this 

 growth they are able to maintain their characteristic form. The 

 growth of the spines and rodlets of Ipomoea appears, therefore, to 

 be of quite the same character as that of the entire membranes of 

 Isoetes, Selaginella, Oenothera and Mirabilis, in which it has been 

 shown that the spore- walls could carry on their growth, altough 

 the protoplast of the spores was not in contact with them. 



Agnes Arber (Cambridge). 



Davis, B. M., Cytological Studies on Oenothera. II. (Ann. 

 Bot. XXIV. p. 631—651. PI. 52—53. 1910.) 



In this memoir the redurtion divisions in the pollen mother-cell 

 and in the ovule of Oenothera biennis are described and figured in 

 detail, and an account of vegetative mitosis in this plant is also 

 included. The author's results are compared with those of Gates 

 and Geerts with which they are in general agreement. The chief 

 point of difference is that while Gates and Geerts describe the 

 chromosomes of the heterotypic mitosis as sub-globular, Davis finds 

 them to have the form of thickened Vs. 



The author regards it as established for Oenothera that the 

 chromosomes of the heterotypic mitosis are not formed side b}' side 

 through the parallel association of two spiremes, but are developed 

 from a Single spireme, which by segmentation forms a chain of 14 

 chromosomes arranged end to end. Agnes Arber (Cambridge). 



Digby, L., The Somatic, Premeiotic, and Meiotic Nuclear 

 Divisions of Galtonia candicans. (Ann. Bot. XXIV. p. 727 — 757. 

 PL 59-63. 1910,) 



Galtonia candicans is a suitable object for cytological investiga- 

 tion, and it has been the subject of much study. There is still much 

 divergence of opinion, however, about the sequence and interpreta- 

 tion of the nuclear phases in this plant, and the present very detailed 

 investigation is an endeavour to put the subject on a clear basis. 

 The author emphasizes the varied character and great inequality 

 shown by the nuclei of Galtonia throughout all the division-figures. 



The main results may be summarised as follows: The chromo- 

 somes in the somatic and premeiotic divisions are formed from the 

 telophase of the preceding divisiön by an alveolation of the chromo- 

 somes and partial Separation of the two sides, followed by a recon- 

 centrution of the same. The parallel threads and portions of linin 

 present in the early heterotype prophases are homologous with those 



