98 



ELEMENTARY STUDIES IN BOTANY 



In the Ferns, with their relatively few and large leaves, the 

 sporangia are borne in large numbers on the under surface of 



the leaf, and usually occur 

 in small groups that look 

 like dark dots or lines 

 (Fig. 76), which are often 

 called " fruit-dots," but 

 of course they are not 

 fruit. In some Ferns al- 

 most all of the leaves bear 

 sporangia, while in other 

 Ferns many leaves are 

 without them. These 

 little groups of sporangia 

 are called sori (singular 

 sorus), and they are very 

 characteristic of Ferns. 

 A section through a sorus 

 is shown in Fig. 77. 



59. The gametophyte. 

 The sporophyte, with its root, stem, leaves, and spo- 

 rangia, seems to most people to be the whole plant. A fern 

 plant, as ordinarily thought of, is simply 

 this sporophyte, and it is certainly a dis- 

 tinct and independent individual. But 

 it bears no sex-organs ; if it did, it would 

 not be a sporophyte. The older observers 

 of plants were puzzled by the absence of 

 sex-organs in Ferns and Club-mosses, but 

 they thought that sex-organs must be 

 present, although invisible. Therefore, 

 they called the group Cryptogams, which 

 means " hidden sex-organs," and since 

 Club-mosses and Ferns are vascular plants, the Pterido- 

 phytes were first called " Vascular Cryptogams," and many 



FIG. 78. Gametophytes of ferns: A, a game- 

 tophyte viewed from the under side (against 

 the substratum), showing the rhizoids and 

 sex-organs, the archegonia (whose projecting 

 necks are seen) being grouped near the notch , 

 and the antheridia being grouped at the 

 other end (in the region of the most con- 

 spicuous rhizoids) ; B, a gametophyte (under 

 surface) from one of whose fertilized eggs 

 (within an archegonium) a young sporo- 

 phyt* is developing, the root being directed 

 downward and the leaf rising upward 

 through the notch. 



FIG. 79. Section of an 

 archegonium of a fern, 

 showing the free neck, 

 and the imbedded 

 venter containing the 

 egg (the large cell). 



