On 20 Nov 2001, at 8:53, toni mettler wrote:

> 1. what are tubers exactly?  examples beyond carrots and turnips?
>

G'day G'day Toni,

   Carrots and parsnips are swollen tap roots.  They are NOT tubers.
Tap roots are central roots which ideally grow straight down.
Umbellifera have tap roots.

 Tubers such as potatoes are swollen underground stems.   Sweet
potato is closely related to convolvulus, a notorious weed with
difficult to eradicate, highly invasive, underground stems.  With
convolvulus the underground stems don't swell significantly but they
still store energy.  When rotary hoed in the market garden the
chopped up lengths of underground stem will sprout forth new plants.

Quentin Grady