What book defines rootstock as "the stock from which the roots, stems
and leaves arise"? You seem to be making up your own definition and
creating a new plant organ, the stock, that is neither root, stem or
leaf.

Gray's Manual of Botany defines rootstock as "a rhizome."
Bailey's Manual of Cultivated Plants defines it as "same as rhizome."
Hortus Third defines it as "subterranean stem, rhizome."
Rost et al's 1979 Botany text defines it as "an elongated,
underground, horizontal stem."

Newer botany texts I consulted don't define rootstock or define it
only in the context of grafting.

You keep saying I "should look at the actual plants first hand." Have
you examined every known species of Dioscorea to determine of they
have tubers or storage roots?

What book defines corm as "A true corm is a tuber covered by a tunic,
as in the Crocus."?
Not all corms have a tunic:
http://virtual.clemson.edu/groups/ho...type.htm#corms

"Tubers" of tuberous begonia and cyclamen do not fit the common
definition of tuber as a swollen
tip of a rhizome. They are enlarged hypocotyls:
http://virtual.clemson.edu/groups/ho...e.htm#enlarged


David R. Hershey





"Cereoid+10" wrote in message ...
Rootstock is the stock from which the roots, stems and leaves arise.
What is so confusing about that?
The old definition is the original correct definition.

You seem to be getting the definition backwards. Stock is the base word to
the term not root. You insist upon making thing far more complicated than
necessary. Maybe you should stick to chocolate bars and stop trying to
confuse everybody. Just because malaprops tend to become common usage by the
great unwashed and eventually get listed in dictionaries, that doesn't mean
they are correct usage of the terms. Common usage can be nothing but bull
shit. Tubers have even been mistaken for bulbs in common usage.

Yes, there is more than one type of tuber even though the terminology has
not been developed to define all of them thoroughly. Various types of tubers
can have the growing points on their surface, forming a ring or restricted
to the apex, depending on the species. A true corm is a tuber covered by a
tunic, as in the Crocus. The tuber of Cyclamen and tuberous Begonias lack
any tunic.

Saying epigeal tubers or tubers in leaf axils are not "true tubers" is
nonsense. There is no reason to believe that tubers can only be subterranean
organs.

As I have said before, you should look at the actual plants first hand
before waxing pedantic over references based on second and third hand
information. You might actually learn something!


David Hershey wrote in message
om...
Rootstock is one of several botanical terms that have multiple
definitions. You seem to be referring to the old gardening definition
of rootstock as a synonym for rhizome or underground stem. Using
rootstock as a term for a stem is obviously confusing and therefore
undesirable.

The more useful definition of rootstock is the root bearing part of a
grafted plant. However, even when applied to grafting, rootstock is
somewhat misleading. Less misleading terms are understock or stock. A
stock may consist solely of root tissue. However, a stock is usually
going to consist mostly of root tissue with a small amount of stem
tissue. The stock of a topgrafted fruit tree will contain considerable
stem tissue. A stock may include an underground stem but usually it
will not. About the only plant with tubers that is occasionally
grafted is potato. Tomato is grafted on potato as a novelty or for
research.

I mentioned several botanical sources, not just Websters Dictionary.
You mentioned no sources. Katherine Esau was a well respected plant
anatomist. The root chapter in her textbook, Anatomy of Seed Plants,
2nd ed. says Dioscorea has "storage roots." Maybe Esau, Hortus Third
and the half dozen college botany textbooks I consulted are wrong and
Dioscorea does have tubers and not storage roots as you contend. If
so, where is some published proof of that? I checked Simpson and
Ogorzally (1986) which says there is controversy whether Dioscorea
storage organs represent stem or root tissue.

Terms for modified stems are not uniformly defined and are often
confusing. There seems to be more diversity in underground stems than
can be accomodated by the handful of terms commonly used. Tuberous
root and tuber are particularly confusing terms. The term storage root
seems to be preferred over tuberous root in botany textbooks and is
certainly more accurate.

There are different definitions for tuber. Some authorities restrict
tuber to a swollen underground organ that develops from a rhizome or
stolon. By that definition, tuberous begonia and cyclamen do not
produce tubers although they are commonly called tubers. Cyclamen is
often referred to as a corm as well. Their storage organs develop
mainly from the hypocotyl and have a vertical orientation, not the
horizontal orientation of a "true" tuber. They are sometimes termed
tuberous stems instead (Hartmann and Kester 1983). However, that term
adds additional confusion. The aerial tubers of some Dioscorea species
are also not "true" tubers and are sometimes termed tubercles or
bulbils.

David R. Hershey


References

Hartmann, H.T. and Kester, D.E. 1983. Plant Propagation: Principles
and Practices. Englewood Cliffs, NJ: Prentice Hall.

Simpson, B.B. and Ogorzally, M.C. 1986. Economic Botany: Plants in Our
World. NY: McGraw-Hill.




"Cereoid+10" wrote in message
...
The term rootsock does not mean the same as true roots. Roostock refers
to
the central body of perennial plants and can be rhizomes, tubers, bulbs,
etc.

Webster's (which is not a botanical reference anyway) is wrong. The
rootstock of Dioscorea is a tuber. Often it is fleshy but it can be
woody
and caudiciform. None have tunicated corms.

You should look for yourself rather than rely on sources based on second
or
third hand information.


David Hershey wrote in message
om...
A rootstock cannot be a tuber because a tuber is a modified stem.

A variety of terms are applied to storage structures of Dioscorea.
Katherine Esau in her Anatomy of Seed Plants text, Hortus Third,
Webster's New Collegiate Dictionary (under yam) and all the college
introductory botany texts I checked all say Dioscorea has a storage
root or tuberous root. Hortus Third also says D. bulbifera produces
aerial tubers, and some Dioscorea species have rhizomes. A few
websites even claim some Dioscorea species do have corms.

Distinctions between types of modified stems, such as stolons,
rhizomes, tubers and corms, are not always clear cut.

Reference



http://www.google.com/search?hl=en&i...orm&btnG=Googl
e+Search


David R. Hershey



"Cereoid+10" wrote in message
om...
Sorry Spammy Davis, Jr. but you have already jumped to wrong
conclusions
and
that does not help.

The rootstock of Dioscorea is a tuber not a corm. A corm is covered
by a
tunic but a tuber is not.

Dioscorea is a huge genus and even includes a number of cold hardy
species.

The "Sweet Potato" Ipomoea batatas is a "Morning Glory" with
tuberous
roots.


I Don't Like Spam wrote in message
...
In article ,
blair wrote:
I was at somebody's house once and they had a big sprawling plant
with
heart
shaped leaves. They said that they grew it by putting a relative
of
the
yam
family into the ground and planting it. Apparently you could also
plant a
yam and grow a different plant as well.

Does anyone know what this plant is?
When I was in college, a friend planted a sweet potato in a pot
and
let it grow. Later she told her room-mate that it was a
"heart-shaped
wandering jew". This was believed until an energetic pet knocked
the
pot over, breaking it, revealing the true nature of the plant. As
mentioned earlier, sweet potato is in Convolvulaceae, with morning
glories.

I wouldn't have brought this up, except sitting on my window sill
here
at work is a member of the yam family Dioscoreaceae, _Dioscorea
macrostachya_, (dormant right now) the leaves of which are very
similar to the heart shaped leaves of sweet potato. This grows
from a
large corm that is quite interesting in appearance. In nature this
corm is hidden underground, but when sold as a houseplant, the
organ
is kept above ground for show (some of the larger, older ones
resemble
a tortoise shell, at least if you have an active imagination).

So, before we jump to conclusions about exactly what the plant is,
there ARE some members of the yam family kept as houseplants that
fit
your description (although, in general, they are a bit pricey, and
not
very common except perhaps through specialty succulent dealers).

Sweet potatoes as sold in the US, often called yams (oh the
wonders of
misleading common names). Ask your friend if they could allow you
to
take a look at the underground stem by brusing away a little soil.
If
it looks like a sweet potato, it probably is. Otherwise, my
Dioscorea
has a THIN, SINGLE, TOUGH twining vine that comes from the TOP of
a
CORM-like structure. If I recall correctly, a sweet potato would
likely have SEVERAL sprouts coming from a VARIOUS POINTS along a
HORIZONTAL TUBER, and those sprouts would tend to be more FLESHY
or
SUCCULENT, at least close to the tuber.

Hope this helps.