220 Cytology and Genetics of the Genus Fuchsia 



mother-cell. The later stages of pollen development were very abnormal, 

 and, whilst the materials for the formation of a pollen membrane were 

 manufactured by the cytoplasm, these were only rarely laid down as 

 a coherent wall. 



In Fig. 26 two pollen grains are represented at a later stage of 

 development. Under a very slight pressure upon the cover-glass, the 

 cytoplasmic body, bi-nucleate in one case and tetra-nucleate in the other, 

 emerged from the imperfectly developed membrane in the manner shown 

 in the sketch. 



Through the kindness of the authorities at the Herbarium at Kew 

 I was able to examine several flowers of 0. ihericuvi Cav. which had 

 been brought from their native habitat in Armenia. In the stamens of 

 all of these perfectly good pollen had developed. 



Whilst working at the John Innes Horticultural Institution I ex- 

 amined the flowers of a plant of G. ibericum growing in the garden of 

 the Institution and to my surprise I found that this developed perfectly 

 fertile pollen grains like those found in flowers from Armenia. 



The Merton plant regularly set seed and I raised a number of seed- 

 lings from it. These I planted in my garden side by side with the sterile 

 specimen and these have regularly, ^^ear after year, produced fertile 

 pollen and set tlieir seed, whilst the sterile plant continued to form 

 stamens containing only abortive pollen. The fertile and sterile plants, 

 apart from the difference in pollen development, were identical in all 

 respects both in their vegetative and floral characters. 



These observations seem to indicate that a plant, fertile in its own 

 homes, when brought under the changed conditions of a different country, 

 may produce offspring some of which are identical with the parent form 

 whilst others are sterile mutants. 



The facts which have been recorded here do not support the view 

 that irregular meiosis and non-fertile pollen are necessarily an indication 

 of the hybrid character of the plant producing them. Cases have been 

 quoted in which undoubted hybrids (e.g. F. puniila x F. alpestris) de- 

 veloped fertile pollen, and showed no irregularities during the meiotic 

 divisions. On the other hand it has been shown that plants which we 

 have every reason to regard as good species, such as Tragopogon -pratensis, 

 may exhibit all the irregularities in pollen development which have b}^ 

 some been regarded as the attribute of hybrids alone. In a third case, 

 that of Geranium ibericum, sterile mutants (as regards the pollen grains) 

 appear to have been developed side by side with offspring which have 

 remained unaltered under the influence of a changed environment. 



