The outer pollen wall, or exine, is more structurally complex than any other plant cell wall, comprising several distinct layers, each with its own organizational pattern. Since elucidation of the basic events of pollen wall ontogeny using electron microscopy in the 1970s, knowledge of their developmental genetics has increased enormously. However, self-assembly processes that are not under direct genetic control also play an important role in pollen wall patterning. This review integrates ultrastructural and developmental findings with recent models for self-assembly in an attempt to understand the origins of the morphological complexity and diversity that underpin the science of palynology.

https://nph.onlinelibrary.wiley.com/doi/pdf/10.1111/j.1469-8137.2007.02060.x

Pollen wall development in flowering plants

CONTENTS. :PAGE Iu~roducgion 113 Ligeraflure review . 115 Me,hods • 116 [~esul~s 1 [7 (i) L . perenne x F. pralcnsis . . . . . 117 (ii) F. pralcnsis x $'1 of L . 1)ercnne x L. pcrcnnc vr~r. mull~ lorum I22 (iii) L. percnnc x F. arl~ndlnacca 129 (iv) Supposed nalural hybrids (JFcsluca loliacca) ]43 (v) F. giganlea × I?. arundinacca 145 Discussiou 147 Chromosomo p~h'iug ~nd chlasm~ frequency 147 Fr~gmen~giou 150 Morphological ~nd physMogic~l ~bnorm~li~ies . 150 Summ~ry 152 References 154

The cytology of certain intergeneric hybrids betweenFestuca andLolium

The tapetum of the anther secretes specific substances at definite stages of development of the enclosed sporogenous tissue, as well as nutrients for its growth and differentiation. Globules with chromatin-like staining properties form at the surface of the tapetal nuclei when the enclosed sporogenous ceils are in a late leptotene stage of meiosis. They are Feulgen-positive, indicating that they contain an appreciable amount of desoxyribose nucleic acid. The globules move from the nuclei to the inner faces of the cells, pass through the cell walls and migrate between the microspore mother cells. The nuclei of the microsporocytes move from a central position to a peripheral one. During the course of this shift in position the loosely paired and somewhat polarized chromosomes become oriented so that the centromeres are adjacent to that portion of the nuclear membrane which is in close contact with the cell wall. The chromatin-like bodies between the microsporocytes collect opposite the regions where the nuc...

The Transfer of Desoxyribose Nucleic Acid from the Tapetum to the Microsporocytes at the Onset of Meiosis

Page 591, line 3 from bottom, for "var. Dunlap" read "var. Dunlap."

Page 597, line 4, for "octaploid" read "octoploid."

Page 602, line 14, for "experimentale" read "experimentale."

Page 603, line 20, for "Viola-arten" read "Viola-Arten

https://www.genetics.org/content/genetics/11/6/590.full.pdf

E. M. Rees

Papers

A Cytological Study of Pollen Development in Lactuca