different from that rendered by the egg and the female, 

 that the very doing of the necessary work of the two 

 sexes results in differences, just as the farmer becomes 

 different from the banker or teacher by giving his time 

 and thought to different things. 



We have seen that the egg cell is large, passive, and 

 highly nourished, while the male cell is minute, poorly 

 nourished, and exceedingly active. When these gametes 

 unite, it is the egg that attracts, while it remains passive, 

 and it is the male cell that is aroused by the presence of 

 the egg and actively seeks out the female cell and unites 

 with it. The role or function of the two cells is different. 

 It is inevitable that the parent that produces eggs, if it is 

 to do its proper motherly work, will become modified in 

 nature and instincts and in structure by producing the 

 eggs and bringing them to the proper condition for 

 fertilization. Similarly, the structures and the instincts 

 demanded of the parent that is to produce sperms will 

 be very different from those of the mother. 



We can thus see that certain internal forces are at work 

 making male parents and female parents different, and 

 that there are duties and tasks suitable to each, so different 

 from the other, that the internal differences will be used 

 and increased by use. 



CHAPTER THIRTEEN. 

 MOSSES AND FERNS 



1. General Grade of Development. Just above the 

 green water plants, called algae, and the colorless fungi, 

 including molds, mushrooms, toadstools, and the like, we 

 find some green plants that begin to look more like the 

 higher plants with which we are familiar. Among these 

 are the mosses and ferns. In them we find for the first 

 time a clear differentiation between roots that take up 

 water, leaves that manufacture food, and stems that 

 connect the leaves and the roots. The lower plants have 

 no such clear differentiation of their bodies. 



The mosses and ferns are not so well developed as the 

 higher seed-bearing plants, but they have so many of the 

 characteristics of the higher plants that no one can get a 

 real understanding of the seed-plants without a study of 

 these lower forms. Furthermore, the method of 

 reproduction in mosses and ferns will help us understand 

 what happens in the higher plants. 



2. The Life Cycle in a Moss. This life history is more 

 complex than anything we have yet described, but it will 

 well repay careful study. 



a. The Germination of the Spore. If we start with a 

 spore, we find that after a longer or shorter period 

 of rest it germinates. This means that the soft, 

 inner living part swells, bursts the old spore wall, 

 and sends out a tube. This tube becomes green, like 

 a filamentous alga, manufactures food, grows, and 

 branches abundantly. The whole thing at this 

 stage is called a protonema, the word referring to 

 its thread-like appearance. This stage is not noticed 

 by most observers, 

 b. Budding. Bud-like outgrowths next appear at 

 various points on these threads. These buds do 

 not grow into new threads like the old ones from 

 which they spring, but divide in such a way as to 



form upright stalks or stems. Each of these stalks 

 develops root-like structures and leaves, lengthens 

 considerably, and becomes one of the leafy moss- 

 plants with which we are all acquainted. 



c. Formation of Gametes and Fertilization. At the 

 top of this leafy stalk there is sometimes a thick 

 cluster of leaves. At the tip of the stem, in the 

 tissues surrounded by these leaves, the moss plant 

 develops two kinds of structures not found 

 elsewhere on the plant. One of these is like a 

 minute flask with a very long narrow neck. This 

 is really a kind of ovary or female organ, and it is 

 celled an archegonium. In the bottom of the flask 

 is a large, plump cell, which is the egg. The other 

 kind of organ that develops at the top of the stem 

 is club-shaped, being attached to the end of the 

 stem by its stalk. This is a male organ and is 

 called an antheridium. When the antheridium is 

 mature it bursts, and from it escapes a great 

 number of minute, ciliated, free-moving cells. 

 These are sperms. The bursting of the antheridium 

 occurs when the end of the stem is moist, as when 

 a drop of dew or rain is among the leaves. Through 

 this moisture the sperms swim about until they 

 come near a fluid secretion produced by the arche- 

 gonium. They are attracted by this secretion. 

 Some of them swim down the neck of the flask, 

 and one of them unites with the egg at the bottom, 

 thus fertilizing it. 



In the moss we have one kind of parent plant 

 with two kinds of sex organs which produce two 

 entirely different kinds of gametes. In other words, 

 the moss described is hermaphroditic. 



d. The Sporophyte and the Formation of Spores. 

 Evidently we now have a fertilized egg. Judging 

 from what we have learned of animals, we might 

 expect this fertilized egg to escape and to develop 

 directly into a new moss plant. But it does not do 

 this. It begins to divide right vyhere it is in the 

 bottom of the flask at the top of the upright 

 stem. It develops a mass of cells, known as a 

 a foot, that connects it with the tissues of the 

 mother plant. Just above this is a delicate stalk 

 that may become an inch or more long, called the 

 seta. At the top of this is a swollen portion, the 

 capsule, in which spores develop. All this develops 

 from the fertilized egg. The whole structure is 

 known as the sporophyte, because its work is to 

 produce spores. It has no leaves and gets the 

 nourishment necessary to grow and mature its 

 spores from the leafy moss plant which is the 

 gametophyte. (See page 000). Within the capsule 

 certain cells by their divisions produce numerous 

 spores; these finally escape from the capsule and 

 the cycle is completed. We are back to the point 

 at which we started, the spore that germinates. 



3. Summary of Reproduction in the Moss. In this life 

 cycle we have found that the moss has three methods of 

 forming more plants, i. e., of reproducing: (1) The 

 formation of spores in the capsule; (2) the budding of the 

 protonema by which erect moss plants are formed; and 

 (3) the formation of the gametes by the union of which 

 the sporophyte arises. (Any generation of plants which 

 produces spores is a sporophyte, but that particular kind 

 of sporophyte we find in mosses is called a sporogonium. 

 The visible parts of all flowering plants are parts of the 

 sporophyte generation.) 



4. The Life Cycle of the Fern. In middle and late 

 summer we find on the under surface of the leaves of 

 oidinary ferns numerous spots. These contain many 



