nly IN THE ORVIS CATALo 
o 
Q 
0 
0 
_l 
s 
o 
CO 
> 
a. 
0 
Ul 
I 
I- 
z 
E 
z 
0 
( WORLD'S 
Coolest 
Shirt 
Popular 
Indian Madras 
4 Colors 
0 
Z 
z 
H 
X 
m 
0 
33 
< 
C/3 
0 
1 
r 
0 
0 
0 
0 
o 
CO 
> 
a. 
0 
LU 
I 
H 
Z 
>i 
Z 
0 
Another of the many distinctive family clothing 
items, gifts home accessories and decorator 
accents you'll find only in the new. Free, full- 
color Orvis Catalog Send now for this very 
special book that will 
fit your lifestyle and 
brighten your days 
SEND TODAY 
FOR YOUR FREE 
COLOR CATALOG 
Name 
Address 
City 
State Zip 
THE ORVIS COMPANY 
125 Years of Sporting Tradition 
161 River Road, Manchester. VT 05254 
0 
z 
m 
0 
33 
< 
03 
o 
3 
r 
0 
0 
>y VLY IN THE ORVIS CATALO 0 
Treasures 
From The Earth 
Color Portfolio of Natural 
Specimens and Catalog 
of Minerals, Display 
Stands. Books and 
Natural Jewelry, $3.00 
Dover Scientific 
Box 601 1C Long Island City, NY 11106 
BUSHNEIL 7x35 CUSTOM 
Mfg. List $280.00 Postpaid $164.00 
This is an example of the deep discount prices on high quality 
optics that is found in our FREE catalog. This catalog lists 
and illustrates an outstanding selection of telescopes, binoc- 
ulars etc , plus valuable information on how to properly select 
them Write for it today 
GIL HEBARD OPTICS 
COURTHOUSE SQ., KNOXVILLE, ILL. 61448 
Plant Parenthood 
Before dispersing, most flowering-plant embryos become dormant. 
Are mother plants protecting themselves from hungry young? 
by Robert E. Cook 
The sight of an animal and its young 
evokes deep feelings in many of us, 
yet we seldom respond to plants in 
quite the same way. A mother plant 
clucking over her clutch of growing 
seeds is difficult to imagine. But in 
an evolutionary sense the provisioning 
of progeny is very similar in plants 
and animals: all mothers will partition 
nourishment and protection among 
their offspring in order to leave as 
many descendants as possible. At some 
point in the development of their off- 
spring, all mothers must also negotiate 
the delicate process of weaning. 
In 1966 the British evolutionary bi- 
ologist William D. Hamilton sug- 
gested that the evolutionary interests 
of the developing embryo are not nec- 
essarily the same as the mother’s. The 
mother’s genetic future is best served 
by maximizing the number of her off- 
spring that survive as successful plants 
in the next generation. Each offspring 
contains the same proportion of her 
genes. Therefore, she should distribute 
her resources evenly among her seeds 
so that each receives sufficient nu- 
trition to provide an excellent chance 
of successful seedling establishment. 
Too much food in any one seed might 
diminish the prospects of all the oth- 
ers. Each offspring, however, may 
have a different interest. Because pol- 
len is promiscuous, each embryo may 
have a different father. It will try to 
maximize its own success, regardless 
of the fate of its kin, by increasing 
its share of maternal sustenance at 
the expense of other offspring and the 
mother. The resolution of this conflict 
of interest between mother and child 
is known as weaning; in plants, this 
process is intimately bound up in the 
development of the seed. 
Seeds are genetically complex and 
are not simply rudimentary plants 
waiting for an appropriate moment to 
germinate. Each seed does contain an 
embryonic individual, which acquired 
half its genes from the mother when 
she formed an egg and half from a 
grain of pollen. This embryo is anal- 
ogous to an animal embryo, but a seed 
is more than a fetal plant. Surrounding 
the embryo is a genetically distinct 
tissue, called endosperm, that serves 
as the source of nutrition for the em- 
bryo. Endosperm, for example, forms 
much of the starchy pulp of corn ker- 
nels and the liquid milk of coconuts. 
Like the embryo, endosperm tissue is 
neither exclusively maternal nor ex- 
clusively paternal in origin. Unlike the 
embryo, however, it develops from the 
fusion of one pollen nucleus with two 
or more maternal nuclei. Genetically, 
it has at least twice as many maternal 
genes as paternal genes; in some spe- 
cies up to fourteen maternal nuclei 
fuse with one set of paternal genes 
to form the endosperm. Therefore, this 
tissue genetically approaches, but is 
not identical with, the maternal tissue 
that surrounds it during development. 
Finally, to guard its contents through 
the journey of dispersal, every seed 
also has a seed coat, a hard covering 
composed of several layers of outer 
tissue. Seed coats, as well as the fleshy 
fruits, pods, and hard shells of many 
species, develop from the maternal tis- 
sue of the flower; their particular qual- 
ities depend entirely upon the action 
of maternal genes. 
If these genetically complex seeds 
were produced asexually, each off- 
spring would be identical to its mother 
and sibs, and there would be no con- 
flict of interest. In sexual reproduction 
involving different individuals, how- 
ever, half the genes of each embryo 
arrive with the pollen and represent 
the evolutionary future of some other 
plant. A pollen grain contributes little 
energy to the raising of offspring; most 
nutrition is maternal. By being para- 
sitic on the nutritional largess of the 
female, the paternal genes achieve 
equal genetic representation in the em- 
bryo while catching a cheap trip into 
the future. Under the influence of 
their paternal genes, individual em- 
bryos may demand more food than 
the mother is prepared to provide. The 
resolution of this conflict lies in the 
intricacies of seed development. 
Traditionally, seed development has 
30 
