H. reverchonii var. serpyllifolia, internode variation along a winter stem:
10 internodes between the yellow bars & shown along the bottom.
23 Jan. 2013, Hays. Co.,

Winter Stem Vestiture in the Hedeoma drummondii complex
by Bob Harms  email-here

Cold season stems exhibit much greater variation in trichome density, length and orientation, in part because starting in very late fall plants produce both types of stems, and most cold-season shoots produce varying vestiture as they elongate (as in the above image). In comparison with warm season stems all 3 taxa have denser vestiture and longer trichomes, these accompanied by very short hairs that curve downward — similar to the summer hairs (note the small hairs in the yellow boxes below). When dense, the vestiture may appear canescent (noted by Irving only for H. reverchonii).

Winter stem pubescence provides a contrast between H. drummondii and both H. reverchonii taxa:

H. drummondii

40x. 18 Nov 2013
Four sections of the same stem. 4 Dec. 2013. Scale 3 mm.

100x. 18 Nov 2013

20 March 2013

20 March 2013

H. reverchonii var. serpyllifolia

9 Feb. 2013

100x. 10 Nov. 2013

40x. 10 Nov. 2013

H. reverchonii var. reverchonii

4 Dec. 2013

24 Oct. 2013
15 Nov. 2013

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