About 70 km north of Madrid is a range of mountains (Sierra de Guadarrama). This was close to a reservoir (Navacerrada) that catches rainfall from the mountains. Altitude about 3000 ft. The plant was in a small clearing next to a path in an oak forest, approx 30 metres from a stream that flows all winter but dries up in high summer. The soil is very sandy. The clearing is about 10 metres in size. Nevertheless, at this time of year there is good light. There are many small wildflowers in the area and apart from oak trees the other vegetation of significant size is broome.
Hope this helps.
Your flower looks to me like a forget-me-not. Flowers of South-west Europe by Polunin and Smythies gives two species Myosotis alpestris and M.stricta which would correspond to the habitat you describe. The flower sizes of respectively 4-10mm and "little more than 1mm" suggest the later.
This is described as "A widespread annual with minute bright or pale blue flowers. Flower stalks less than 2 mm. calyx with deflexed hooked hairs and adpressed staight hairs at base, divided halfway into lobeswhich are closed in fruit and not deciduous. dry sandy places C.&E. Spain.
There is only a picture of alpestris and this is in Polunin - flowers of Europe and it looks very similar to yours.
I hope this helps.
Myosotis: Hmmm, I'm not sure sure. There's no pale ring at the mouth of the corolla, and the petals are a bit gappy (not touching/overkapping).
I think it might be elsewhere in the Boraginaceae, eg. a species of Buglossoides (Lithospermum).
(Boraginaceae is in Vol.11 of Flora Iberica)
I think Mike is correct that it is not forget-me-not. I have images of forget-me-nots taken nearby (see http://www.nhm.ac.uk/natureplus/message/28758#2875) and the plant looks quite different and the leaves are not curled as in the plant in question, though the leaves are not visible in that photo. Here's another photo of the forget-me-not which shows the leaves.
I have found another plant in the Borage family which is very small flowered. Buglossoides incrassata. It was mentioned in the Floraiberia website and there are pictures if you Google it. For some reason I can't find it in any of my southern Europe flower books.
Thanks for looking. My wife is the plant expert in our family and she isn't here right now but I know what you mean about books. She has 9 books which should cover the wild plants of Europe, Southern Europe, Iberia etc and she's often found plants that simply aren't in the books.
The flower of the incrassata does look similar but the leaves don't resemble at all, do they? One thing I have learnt from her is to check out the leaves. Besides which, it seems incrassata is quite a big plant - the one I photographed couldn't have been more than 2 cm above ground level at any point.
Also, one has to be so careful when Googling. I just Googled for images of Buglossoides incrassata and found the photo of my plant straight off this thread in NaturePlus - simply because you offered it as a possible identification. I bet it also comes up for forget-me-not as well!