106 
 
 
ALDO LEOPOLD AND SARA ELIZABETH JONES 
 
 
   (1) Any given aggregation of data is subject to 
numerous possible errors, only part of which can be 
identified. 
   (2) The more species, the more years, the more 
stations, and the more observers behind any given 
deduction, the greater the chance that errors will 
compensate. 
   (3) During the decade here treated, the degree of 
error declines progressively. 
   (4) Phenology of the (b) type (fixed stations) 
avoids some errors. 
   (5) Caution is necessary in attaching significance 
to differences of small magnitude. 
 
                  PLANT GROUPS 
 
   Those who work with soil, crops, wild plants, wild 
animals, or landscapes sometimes wish to know what 
plants may be expected to be in bloom, or in fruit, 
at a given time. For their convenience such data 
have been segregated in diagrammatic form, in 
Figures 1, 2, 3, 4, and 5. These assemblies present 
an average of the two stations, and ignore devia- 
tions due to early or late years. They include some 
 
 
Ecological Monographs 
        Vol. 17, No. 1 
 
 
species which are omitted from Tables I to 12 be- 
cause the record is too short. 
   The point of each arrow is the beginning date, and 
the length of the arrow is the duration of the event. 
   By projecting a vertical line through any given 
date, the reader can tell at a glance what species 
are likely to be in bloom (or in fruit) on that date. 
   It is perhaps of interest to note that all four 
groups of flowers describe, in their succession of 
"arrow points," a reversed "S" curve. The groups 
differ only in the degree of curvature, and the dates 
of inflexion. Woods flowers inflect in May, prairie 
and sand plants and weeds in June (with some minor 
undulations) and marsh plants in July. The shape 
of these curves is of course affected somewhat by the 
local assortment of sites and species, and by the 
degree to which all are covered. 
 
                   WOODS FLOWERS 
 
  Figure 1 assembles some of the wild flowers charac- 
teristic of oak-hickory, climax hardwood, and oak- 
jack pine woodlands at their point of confluence in 
this region. 
 
 
April           May            June            July            August   
     Seotember        October 
                -o 8n 14 /9 2rn            - 8ai 13l /8 20 -f 28 2 11912/792Z0211/
// /6~ 2126 / // 16 2A~19A'26 
 
 
(Ser.tica americam 
ale Breeches (Dico 
oot (Sanguinaria 
Mort (Dentaria l& 
.rly Meadow Rue (T] 
'ood Anemone (Anem 
Bellwort (Uvulari, 
Togtooth Violet 
  Arabia (Arabis I 
    White Trilliw 
    Nodding Tril: 
    Wake Robin 
    Jacobs Lead, 
      Blue Phlox 
      Jack-in-tia 
      False Sol 
         Wild Go,, 
         Wateri, 
           Tell" 
             _Ue~ 
 
 
4 
atra Cucullaria) 
 
 
%uadensis) 
 
 
Entata) 
tlietrum dioicum) 
ie quinquefolia vi 
grandiflora) 
-,rythronium albidi 
ýummondi) 
(Trillium grandi: 
Lum (Trillium Glee 
ýrl11ium recurvatu 
or (Polemonium rei 
Phlox divaricata) 
-pulpit (Arisaema 
non's Seal (Smilam 
mium (Geranium mn 
if (1idro hllum 
Lodi'e Slipper ( 
cpple (Podophyllui 
ot Cicely (Osmorh 
n Cryptotsenta (C 
.False Spikenard 
   Cmaada Mayflol 
   Black Snakeroi 
     Solomon'. Se 
            Ana 
 
 
,.interion WOOD FLOWERS 
                     LEGEND 
                         In bloom 
 
Lor)   ---Stroggling bloom 
 
 
loni) 
 
Lane) 
 
 
wriphyllum) 
Lna stellata) 
miatum) 
Lrginianum) 
,yripedium parvidf 
peltatum) 
ca Claytoni) 
,ptotaenla canadeni 
(Smilacina racemoi 
or (Matanthemom caj 
ý'(Sanicula marllma 
11 (Polygonatum bi: 
)no (Anemone virgii 
,eum (Geum canaden, 
   Enchanter.s 1id 
   Tick Clover (1 
      Zopseed (Ph: 
      Jewelweed 
 
 
.4 
 
 
0m"m var. pubescenl 
 
 
 
is) 
a) 
adense) 
dice) 
lorum) 
Ian&) 
0)    __ 
htshade (Circlea 1I 
esmodium scuminatuz 
ym Leptostachya) 
(Impatiens pallidal 
 
 
Cardinal Flower (IA 
White Snakeroot (] 
 
 
tifolia) 
 
 
bellsCardinalis) 
upatorium ragosua 
 
 
Fio. 1. Average Blooming Periods of 34 Woods Flowers. 
 
 
Sepatice 
  Datchn 
  Blood 
     Too 
 
 
/0 - ., .5 .  - 
 
 
J 
 
 
V