142 
E. N. Thomas. 
cotyledonary node, the extraordinary development of the “collet” 
in the cotyledon being accountable for the apparent variability 
in the position of the tuber. 
The anatomy of these forms is very interesting and Conopodium 
denndatum and Anemone apennina are remarkable on account of the 
presence of complete root structure in the lower part of the petiole 
of the cotyledonary member. 
Genetics. 
The meetings of Section K were opened in Melbourne with an 
address by Miss E. R. Saunders, entitled “The Double Stock: its 
history and behaviour.” There is no record of the double form until 
the middle of the 16th Century, and we are probably justified in 
supposing that it did not exist long before that date, although the 
Single Stock dates back to Greek and Roman times. 
The possibility of obtaining doubles from the seed of singles 
—the doubles themselves being sterile—was not realized for more 
than a century after their cultivation, and the usual mode of 
propagation was by slips or cuttings. Suggestions for increasing 
the number of doubles have always failed under experiment, and 
the reasons are obvious now that we know their Mendelian relation, 
ship. Nevertheless, it is possible by appropriate selection of seed 
or plants to obtain an increased number of doubles in the bed as 
a whole. 
This was followed by a paper by Dr. Bond, on Sex Dimor¬ 
phism and Secondary Sex Characters in some Abnormal Begonia 
Flowers, and on the Evolution of the Monoecious condition in 
Plants. The author apparently assumes the dioecious condition 
to be the most ancient, and regards the hermaphrodite as produced 
in response to insect fertilization with the monoecious as an 
unstable intermediate condition. Sex differentiation usually occurs 
in such a way as to give central terminal femaleness and peripheral 
lateral maleness as in the normal hermaphrodite flowers, and in 
many inflorescences, and even in abnormal flowers such as those of 
the Begonia, particularly studied by Dr. Bond. These show 
associated secondary sex characters such as abnormal floral bracts, 
etc. The author contrasts the comparative inconstancy of secondary 
sex characters among plants with the much greater interdependence 
of these with the primary secondary sex characters among animals, 
and suggests that this may be due to the much more restricted 
action of sex hormones among plants. 
