EVOLUTIONARY TRENDS OF FLOWERS

©David B. Fankhauser, Ph.D.,
Professor of Biology and Chemistry
University of Cincinnati Clermont College,
Batavia OH 45103
Squirrel Corn and Dutchman's Breeches
Blood Root,
a more primitive plant
This page has been accessed Counter times since 7 April 2003.

rvsd 31 March 2000, 4 April 03
Squirrel Corn and 
Dutchman's Breeches,
two advanced plants

A number of trends in the development of flower morphology can be noted since angiosperms appeared on earth.  The following table lists four major trends, and gives picture examples of each trait (all examples taken by DBF in SW Ohio.)

TRAIT
PRIMITIVE
ADVANCED
1. number of flower parts many, indefinite parts  few parts, fixed numbers
Bloodroot has indeterminant
number of petals and stamen

Spring Cress has four petals
and six stamen

2. relation of parts separate fused
Apple has five distinct petals

Ground Cherry has five fused petals

3. symmetry of parts  radial bilateral
Horse Nettle has radial symmetry

Common Blue Violet has
bilateral symmetry

4. location of ovary superior inferior
Bloodroot has a superior ovary
 (positioned above the petals)

Ground Ivy has an inferior ovary

Here are nine common families of plants with which students should be familiar.
 
Family
traits
examples
Page in
Peterson's
Fieldguide
toWildflowers
White Trout Lily                White Trout Lily

Snow Drops                  Yellow Trout Lily
Lily parts in 3s:
3/6 petals,
6 stamen,
3 lobed stigma
lily,
onion
xvi
Spring Cress                    Cut- Leafed Toothwort
Cruciferae 4 petals in a cross,
6 stamen
(2 are shorter)
cabbage,
mustard
xix
Apple                                Cherry
Rose 5 rounded petals,
5 sepals, indefinite
number of stamen
berries,
apple,
cherry
xx
Sweet Pea
Legume 5 petals, 2 lower:
2 in keel, 2 wings,
1 upper banner
beans,
peas
xx
Common Blue Violet          Smooth Yellow Violet
Violet parts in 5s,
lower petal wide,
veined
pansy,
violet
xxii
Pepper and Salt             Golden Alexanders 
Pepper and Salt
Umbelliferae umbrella-shaped
clusters, 5 petals
carrot,
Queen Ann's Lace,
poison hemlock
xxiii
 Purple Dead Nettle       Ground Ivy
Labiatae corolla,
2 flaring lips,
upper has 2 lobes,
lower three lobes
mints xxv
Horse Nettle                     Virginia Ground Cherry
horse nettle
Solanaceae parts in 5s,
stamen and pistil
united to form
beak.
forms berry
w/ many seeds
Tomato,
potato,
egg plant
xxv
Dandelion                                Wingstem
Dandelion
Compositae cluster of many florets, rays around
central disk
largest family,
daisy,
zinnia,
dandelion
xxviii

In comparison of Monocots and dicots in Campbell's 6th:
Summary table 721
Seed Structure 792
Seed Germination 794
Stem structure 733
 
page 721 in Campbell's 6th MONOCOTS 
DICOTS: 
example: corn (or wheat, above) bean (or alfalfa, above)
seed leaves (792, 793 & 794) one two (here is a bean seedling)
vascular tissue distribution (733) complex distribution arranged in ring
leaf structure (721) veins usually parallel veins reticular
root structure fibrous or diffuse tap root
flower parts multiples of three parts in 4s or 5s