﻿1903] CURRENT LITERATURE 37 1 



The developaient of the spores in Selaginella has been investigated 

 by Denke."" As is well known, Selaginella is a refractory object for CMC- 

 logical work. Denke recommends for fixing a mixture of one-third acetic 

 acid and two-thirds absolute alcohol, and Haidenhain*s iron-alum haematoxy- 

 lin, with or without Congo red, for stahilng. He finds that the cauline 

 sporangia originate from epidermal cells and underlying tissue. In the 

 microsporangium a considerable number of spore mother cells fail to undergo 

 the tetrad division. Such cells lose protoplasmic contents and function like 

 tapetal cells, Microsporangia and megasporangia develop alike up to the 

 spore mother cell stage and in phylogcny probably represent a common struc- 

 ture. In both microspore and megaspore mother cells the spindle is extra- 

 nuclear in origin, and it appears while the nucleus is still in the resting stage. 

 The spindle soon becomes bipolar and in its behavior recalls the spindle in 

 the spermatogonia of the salamander. The formation of the membranes of 

 the four young spores is peculiar, and, in spite of the attention which has 

 been given to the subject, a conclusive account has not yet appeared. From 

 the cytoplasm of the young spore, two membranes are formed one after the 

 other. At first they grow in contact with each other, but the outer membrane 

 by a more rapid growth becomes separated from the other, and a space appears 

 between them. The inner layer — the mesospore — does not arise by a mere 

 splitting of the outer layer, or exospore, as some have supposed. The deli- 

 cate wall formed around each of the four young spores at the division of the 



spore mother cell is dissolved. — Charles J. Chamberlain. 



Gtjignard" has obtained some very interesting results from a study of 



Hyp. 



Incidentally triple fusion 



was found to occur in the embryo sac, and the antipodals show that increase 

 in size and prolonged activity characteristic of the antipodals of Ranuncu- 

 laceae ; but the chief interest centers in the unusual formation of the proem- 

 bryo. The first division of the fertilized t^g is transverse, as is usual, but by 

 the enlargement of the basal cell the apical cell is thrust somewhat to one 

 side and in this position divides at right angles to the first division. At first 

 the two daughter cells of the second division are equal in size, but soon the 

 upper one begins to enlarge, and becomes pyriform and approximately paral- 

 lel with the origin basal cell. The three-celled proembryo thus consists of 

 two large and inflated and presently vacuolate basal cells, lying side by side, 

 and a small embryonal cell resting between them at their free ends. The 

 two basal cells thus form a suspensor of most unusual origin, and remain 

 very prominent and active during the slow development of the embryo, 

 which is somewhat peculiar, in that it is not initiated by the longitudinal 

 vision of the embryonal cell, but by transverse divisions the embryo becomes 



'"Denke, P., Sporenentwickelung bei Selaginella. Beihefte zum Bot. Centralbl. 

 12:182-199. ph^ J. 1902. 



"GuiGNARD, L., La formation at le developpement de rembryon chez I'llype 

 \ coum. Jour. Botanique 17: 33-44./^^. 21, 1903. 



di 



