81 
FLOWER STRUCTURE AND THE CLASSIFICATION OF DICOTYLEDONS 
—_ 
3y ALFRED GUNDERSEN 
Studies of flower structures were continued, with many draw- 
ings made by Miss Maud H. Purdy, including a detailed color 
study of the floral development in Blionenbachia insignis. Other 
possible relatives of Cactaceae have been studied, such as Mesem- 
bryanthemum and related genera. The linear colored parts of 
this group of genera are usually referred to as sterile stamens, 
sometimes as petals. The methods of attachment of the fertile 
and sterile stamens vary in an interesting manner in different 
species and show the common origin of these structures. In 
Nymphaea we have a series of transitions from stamens to petals 

often illustrated. The characters of Mesembryanthemum are very 
suggestive also of Cactaceae and Myrtaceae. In many Myrtaceae, 
or example Leptospernui incanum, the bases of the stamens are 
fused. Such fusion is not necessarily an advanced character, as it 
occurs in the fossil Cycadoidea. A change of Cactaceae to a 
more primitive position would involve many other families. 
Other groups of which drawings have been made include 
Hamamelidaceae, Cornaceae, and Betulaceae; these families have 
many characters in common. A question in this connection is 
the number of ovules per flower. The ancestors of angio- 
sperms were certainly wind-pollinated; with this goes usually 
numerous pollen grains and relatively few ovules. But few ovules 
or a single one is also often the condition of the flowers in which 
pollination by insects has been highly perfected. Similarly, basal 
placentation may be either a primitive and an advanced character, 
depending on the group. 
A background for the Engler System of classification was 
Kichler’s work on floral diagrams (1878). Eichler’s diagrams, 
widely copied, are nearly all of cross sections of flowers. For the 
purpose of showing the attachment of parts, longitudinal sections 
are more suitable. Toward the end of the year a chart was pre- 
pared showing such sections of stamens and carpels in thirty-five 
families of dicotyledons with possible relationships indicated. The 

chart with accompanying text will be published soon. 
