Cali, I understand your going back between C. flammula and C. vitalba. I always thought what I see growing alongside the roads near our place was C. flammula. Yesterday I went out to collect some seeds, at the first stop I suddenly realised the seeds were not those of flammula, but vitalba, and when I looked at leaves, I saw that they were larger. The seeds of C. vitalba were much smaller, but the white 'fluff' (the silky fruit appendages) were much longer, so 'The old man's beard' was really appropriate. A few hundred meters further up, where I collected seeds before, I found both of them growing side by side. Next year I will have a closer look at the flowers and see if I can see a difference. So thank you, I learnt something new yesterday.