234 Nichols, A morphological study of Juniperus communis var. depressa. 



The tapetum persists until after the formation of prothallial 

 tissue. 



From four to ten archegonia are organized, and, as in the 

 other Cupresseae, these form a Single complex which is surrounded 

 by a layer of jacket cells. 



Peculiar aster-like structures, termed asteroids, are conspicuous 

 in the central cell of the archegonium and persist until after fer- 

 tilization. Their function is obscure. 



The division of the central cell nucleus takes place about 

 three days before fertilization and is approximately simultaneous 

 in all the archegonia of a group. The spindle of this division is 

 apparently entirely of intra-nuclear origin. 



A true ventral canal cell is never formed. The ventral canal 

 nucleus usually disintegrates, but sometimes persists for a long time, 

 and may divide mitotically. 



In the mature egg nucleus the most conspicuous features are 

 the nucleoli and pseudonucleoli. Some of the latter are presumably 

 related in some manner to the chromatin. 



Fertilization takes place in June, and an interval of a 

 week may elapse between conjugation in different flowers on the 

 same plant. 



Both male cells may be functional. 



The entire male cell may enter the egg, but frequently the 

 cell membrane is cast off outside. 



The male nucleus and the egg nucleus apparently fuse while 

 in a resting condition, and the fusion nucleus becomes surrounded 

 by a mantle of starch derived from the male cell. 



No distinction between male and female chromatin is apparent 

 until the Organization of the spirems of the first segmentation di- 

 vision, when two separate masses of chromatin may be clearly 

 distinguished. 



The spindles of the first division of the fertilized egg and of 

 the foEowing divisions are intra-nuclear. 



Usually eight free nuclei are formed before the appearance 

 of walls, but in exceptional cases wall development is delayed until 

 after the fourth nuclear division. 



Cell divisions in the upper tier of cells of the proembryo give 

 rise to the suspensors and the cells of the rosette. 



Note: Since the completion of this work there has appeared a paper by 

 Miss A. M. Ottley on "The development of the gametophyte and fertilization 

 in Juniperus communis and Juniperus virginianaP . (Bot. Gazette 48 : 31 — 46.) 

 In the main her results are in accord with those of the writer. She describes, 

 however, the formation of a distinct stalk cell (p. 34), a structure which the 

 investigations of the writer have failed to demonstrate. Also the fact should be 

 noted that the mature male cells are spherical, not hemispherical (1. c. p. 35). 



