'Anonymous' gave the right answer yesterday, when I had already written the first draft of this post. The 'paintings' I showed last week were in reality photographs of glass works of art displayed in natural surroundings. The artist who made them is called Dale Chihuly, whose work I found by traversing the internet looking for alien plants. I rather like the plant shapes he produces: they are very organic looking, and displaying them among real plants provides a pleasing contrast. I thought that showing them in their original form might have made the riddle a bit too easy, which is why I turned them into 'paintings'. I did so with Corel Painter, by the way.
Above are the three images I had worked over, but now as I found them on Mr Chihuly's website, right here. There are two more I did not work over to give you a further taste of his work. If you wish to see more images of his plant-like creations, you will find many more of them under the column 'temporary' of the 'installations' page; just pick something from the right-hand column and have a look.
After this intermezzo I will be back with a post about legs, discussing things such as why splaying them works for very small animals but not for large ones, and why bones of large animals have a tendency to fold in zigzag fashion.