What can you tell about germination, about osmosis, and about photosynthesis? Do you remember what protoplasm is? Protoplasm comes from Greek words that mean "first made." In older books like Fairy-Land of Science, the meaning of protoplasm can sometimes be confusing. This is what you need to know: Protoplasm is the whole content of a cell enclosed within the cell membrane, including both the cytoplasm and nucleus. Cytoplasm is the content of the cell except for the nucleus, and you will probably hear more about cytoplasm if you look at newer books and websites. They both mean the living contents of a cell that is surrounded by a plasma membrane; that is, most of the stuff inside a cell. What is cytoplasm made of and what does it look like? It is a thick liquid or gel, made up of about 70% to 90% water, and usually colorless. What is it for? It is within the cytoplasm that most cellular activities occur, including processes such as cell division, which is what makes the plant grow.
If you can't imagine that, look at any diagram of what's inside a plant cell. The cytoplasm is the stuff that all those other little things are floating in. Making Jell-O simulations of this has become a popular science-class activity (photo below from that link)--do you want to try it?
One other question--do you know what ammonia smells like? Sniffing ammonia is dangerous, so I'm not going to tell you to go smell some; but if you have any glass cleaner around, maybe you could sort of smell it at at a safe distance. Ammonia may be dangerous for us, but it's good for the plants...well, actually what they need is nitrogen, but they get that from ammonia..
Now on to the lesson.
Look at my plant again, and tell me if we have not already found a curious history? Fancy that you see the water creeping in at the roots, oozing up from cell to cell till it reaches the leaves, and there meeting the carbon which has just come out of the air, and being worked up with it by the sun-waves into starch, or sugar, or oils. So we have hydrogen, oxygen, and carbon all meeting up in the plant.Narration to follow.
But meanwhile, how is new protoplasm to be formed? for without this active substance none of the work can go on. Here comes into use a lazy gas we spoke of in an earlier chapter. There we thought that nitrogen was of no use except to float oxygen in the air, but here we shall find it very useful. So far as we know, plants cannot take up nitrogen out of the air, but they can get it out of the ammonia which the water brings in at their roots.
Ammonia, you will remember, is a strong-smelling gas, made of hydrogen and nitrogen, and which is often almost stifling near a manure-heap. When you manure a plant you help it to get this ammonia, but at any time it gets some from the soil and also from the rain-drops which bring it down in the air. Out of this ammonia the plant takes the nitrogen and works it up with the three elements, carbon, oxygen, and hydrogen, to make the substances called albuminoids, which form a large part of the food of the plant, and it is these albuminoids which go to make protoplasm. You will notice that while the starch and other substances are only made of three elements, the active protoplasm is made of these three added to a fourth, nitrogen, and it also contains phosphorus and sulphur.
And so hour after hour and day after day our primrose goes on pumping up water and ammonia from its roots to its leaves, drinking in carbon dioxide from the air, and using the sun-waves to work them all up into food to be sent to all parts of its body. In this way these leaves act, you see, as the stomach of the plant, and digest its food.
When Arabella Buckley talks about things like "little mouths" on plants, you might think that she is just doing more Victorian fairies-of-science talk. But in this case she's quite right: the leaves of plants do have openings that are very much like little mouths. If you don't believe it, look at this close-up of a lavender leaf. Makes you almost afraid to go out in the garden.