Galeopsis tetrahit [Brittlestem Hempnettle]

[Andrea B.]

Blum, A. G. (2014) Galeopsis tetrahit L. (Lamiaceae) Brittlestem Hempnettle. Flowers photographed in ultraviolet and visible light. http://www.ultraviol...tem-hempnettle/

 

Southwest Harbor, Maine, USA

18 July 2014

Wildflower

 

Synonyms:

• Common Hemp-nettle
  

Comment:

The sturdy, square-stemmed G. tetrahit can grow almost anywhere but is commonly found on newly disturbed land where it is a first colonizer. It has medicinal uses but can be poisonous if not proberly handled. The flower has the typical two-lipped appearance of so many lipped flowers in the Mint family. The lack of a notch on the lower lip edge differentiates G. tetrahit from its cousin G. bifida. The stem is swollen below the joint.

 

In UV appearance the outer surfaces of the flower are UV-dark. The inner lower lip is UV-dark. The inner area of the upper lip around the four stamens is much lighter in UV. The bumpy surface of the lower lip appears velvety indicating the presence of conical cells which likely provide a grippable landing surface for pollinators.

 

Reference:

1. New England Wild Flower Society (2014) Galeopsis tetrahit L. Brittle-stemed Hemp-nettle. https://gobotany.new...opsis/tetrahit/

 

Equipment [Nikon D600-broadband + Carl Zeiss 60mm f/4.0 UV-Planar]

 

Visible Light [f/11 for 1" @ ISO 100 with onboard Flash and Baader UVIR-Block Filter]

This is a composite of two photos which were stacked for increased depth of field.

Please click the photo for a larger view.

 

Ultraviolet Light [f/11 for 20" @ ISO 400 with SB-14 UV-modified Flash and Baader UV-Pass Filter]

This is a composite of two photos which were stacked for increased depth of field.

Long exposures were taken so that the UV flash could be fired multiple times for even lighting.

Please click the photo for a larger view.

 

Visible Light [f/11 for 1/2.5" @ ISO 100 with onboard Flash and Baader UVIR-Block Filter]

A cutting from the plant gives an overview of its structure.

 

Visible Light [f/11 for 1/4" @ ISO 400 with onboard Flash and Baader UVIR-Block Filter]

Just below the axial node the joint is slightly swollen on the hairy stem.

 

Visible Light [f/11 for 1" @ ISO 400 with onboard Flash and Baader UVIR-Block Filter]

Four seeds are developing in the ovary.