Purple toothwort. French Lathrée - Latin -Lathraea clandestina.
When a friend asked 'Are they crocuses ?' I saw that he needed some botanical formation (instruction) , as the French would say. These brilliantly purple flowers, growing in damp places at the base of poplar or willow trees, have no connection at all with crocuses. The form of the flower is more akin to that of a snapdragon. In much of the west of France they are common in April and May. They do not grow in the east, nor in most departements in the north. In some districts they are spectacular and cannot be overlooked. The books yield no common French name, other than that borrowed from the botanical Latin. One reader tells me that it has the name of La Triste Voyageur. Very rarely, you may find the flowers in some notable gardens in England. It has escaped and is now found there in the wild in a few locations. The plants are very difficult to establish in cultivation. That is because of their unusual biology. The plant is a parasite on the roots of the trees. It is almost impossible to transplant it so that it will attach itself to the roots of the host. The most sensible method is to germinate the seeds next to the roots. How can that happen in nature? The fruits are large capsules, a centimetre across which, when ripe, burst explosively. Inside are seeds huge for the size of the plant. Each capsule has about four seeds. Each seed is towards half a centimetre in diameter. They float and this is probably the way the seed is normally distributed. The seed ends up against some roots of the willow or poplar and there germinates. A young root of the toothwort penetrates the tissues of the host and the next generation of toothwort commences. The only remnants of the leaves are found underground on thick stems. They are white and shaped like teeth ; thus the name. But even these leaves are odd. The question has been asked amongst botantists How does water move in the toothwort? That is not so strange a question. In all green plants water evaporates from the leaves and in so doing there is a water column sucked from the soil to the topmost height. Toothworts have no leaves to generate this flow. The hollow cup formed to the inside of an underground leaf is always moist and oozing water. Possibly glands push out the water and thus generate a flow from the roots of the host carrying with it the essential nutrients.
There is a far more common relative in the northern regions of Europe. This is Lathraea squamaria the common toothwort. It is a dirty white in colour everywhere, so is more likely to be overlooked. That species most usually parasitises the hazel tree.