a bit of botany : 2 / stipules

 

Stipules are foliate appendices which grow usually in couple to the base of leaves  petioles (in Dicotyledone plants)

Leaves of the Begonia genus plants are always stipulate.

Persistence and stipules margin are not useful characters for belonging to a section.

 

 Two important characters about stipules :

  1. persistence
  • persistent : when they are still present when the leaves are totally grown, we say the stipules are persistent  (they sometimes fall only after the leaves fall)
  • caducous  if not, we say they are caducous (or deciduous) ; stipules are often early caducous

B. mazae  f. viridis  Ziesenhenne / Gireoudia section / Mexico /  persistent stipules

B. eminii Warburg / Tetraphila section / Tropical Africa (from Nigeria to Angola) /  early caducous stipules, faded

  1. margin
  • entire : margin is entire if it has not any incision
  • dentate : if it is no entire, it is dentate

B. chlorosticta Sands / Petermannia section / Malaysia (Borneo Sarawak) / stipule with entire margin

B. auriculata JD Hooker / Filicibegonia section / Gabon / dentate stipules

 

We can sometimes see other characters about stipules :

the shape which is very varied :

  • triangular :

B. mazae  var. mazae Ziesenhenne /  Gireoudia section / Mexico / triangular and acuminate stipules

B. convalloriodora C. de Candolle /  Ruizopavonia section / Mexico – Central America / acuminate stipules

  • elliptic-ovate:
  • acuminate : narrows progressively and stops suddenly in a slender point
  • cuspidate :  subsided in a sharp and tight point which does an angle with the margin
  • long attenuated :
  • navicular or boat-shapped : as a boat or a shuttle
  • the two stipules are sometimes different, the outside one wraps the inside and the treminal leaf bud

B. mannii  WJ Hooker / section Tetraphila / de la Guinée au Gabon / the outside stipule wraps the bud of the future leaf and the inside stipule

  • they have sometimes a median promient nerve with a fold on this nerve 

B. venosa Skan / Begonia section / Brazil / stipules with a median nerve prominent

 

the margin

  • denticulate or serrate : with small teeth as a saw.
  • fringed :  margin densely and finely serrate
  • ciliate : the margin has hairs often in line with the margin teeth

B. Philippines sp. / stipule margin finely dentate and ciliate

 

the outside surface :

  • which may be glabrous or ciliate on the whole outside surface

B. listada LB Smith & Wasshausen /  Pritzelia section / Brazil – Paraguay – Argentina / stipules totally hairy