Fwd: Re: Different codes (and eudicots)

[Philip Cantino]

Ken Kinman wrote:

>>       Correct me if this non-botanist is wrong, but isn't it relatively easy
>>to distinguish a monocot from a dicot using a combination of simple
>>characters (just one or two characters will usually do, except for some
>>paleoherbs).


Curtis Clark wrote:

>Not as easy as the botany texts might imply. A suite of features
>distinguishes the "strict monocots" (grasses, lilies, orchids, and their
>ilk) from the eudicots. And those make up the literal bulk of the plants
>that most people encounter, especially outside the tropics. But only a
>single character is uniformly diagnostic, the cotyledon number. There are a
>number of examples of dicots with atactosteles, monocots with "reticulate"
>leave venation, dicots with flower parts in 3 (even among the eudicots),
>and monocots with persistent  seminal root systems. The loss of secondary
>growth in monocots seems to diagnose the same group as the single
>cotyledon, but there are among the dicots some purely herbaceous species,
>as well.

Even the cotyledon number does not reliably distinguish monocots from
dicots.  At least one dicot (Claytonia virginica) usually has only
one cotyledon (see J. Arnold Arboretum 50: 588 (1969)), and I am told
there are other exceptions as well.

Phil


Philip D. Cantino
Professor and Chair
Department of Environmental and Plant Biology
Ohio University
Athens, OH 45701-2979
U.S.A.

Phone: (740) 593-1128; 593-1126
Fax: (740) 593-1130
e-mail: cantino at ohio.edu