The silk weeds, _Cladophora Glomerata_ are somewhat similar in appearance to the plant we have just described, but they are denizens of running streams rather than of ponds. They are the green thread-like plants we so often see attached by one end to rocks and stones beneath running water. Each plant consists of a long, cylindrical structure composed of several cells. We mention the silk weeds here, because they are best of all plants for showing cell growth. This growth takes place at or near the unattached end of the plant and is easily observed. The end cell may be watched for the process. Its green contents will be observed to contract in the middle so that it assumes an hour-glass shape. Then, where the contraction has taken place, we can watch the formation of a wall right across the cell, so that when the process is completed we have two cells where formerly there was one. More rarely, the contents of a cell will be observed to bulge out a side wall, then a new wall is formed to divide it off from the main cell and thus the beginning of a branch is formed. The silk weeds exhibit no movements, except such as are imparted to them by the running water. A very beautiful little pond plant is known to science as _Draparnalda Glomerata_. We shall probably forget its name, but we can never forget the plant itself when once we have been fortunate enough to see it. A single row of large, transparent cells, containing very little green colouring matter, forms the main part of the plant. At regular intervals from these transparent cells, there arise rings of deep green branches, each one tipped with an extraordinarily long, colourless hair. _Draparnalda_ is indeed a plant worth looking for. Two common little green plants grow so near to the edges of ponds that they may well be included amongst our pond plants. The simpler of the two, known as _Vaucheria Sessilis_ thrives on almost any damp soil and may even form a covering on soil in pots. In structure, _Vaucheria_ is very simple for it consists of a single, frequently branched, tubular cell. The little attaching organ, by means of which the plant fixes itself to some firm support, is colourless, so too is the tip of the cell where growth takes place. We must examine this little plant when we come across it and we must not fail to notice that it is composed of but one cell. The only time at which we can find any cross walls, is when _Vaucheria_ is about to increase. Then the tip of the cell swells, like a little club, and a cross wall separates it from the rest of the plant. The contents of this cell rounds itself off, becomes fringed with innumerable little lashing whips and escapes from a pore at the tip of the cell in which it was formed. This little organism swims about for a time in the water, for _Vaucheria_ only increases in this manner when it is under water, at length it comes to rest and forms a new plant.