226 



General Biology 



to hold the plant in place and absorb moisture and food material from 



the ground. 



This minute plant, which de- 

 velops from the spore, is called the 

 prothallium ( ). It 



is often heart-shaped. A portion 

 just posterior to the notch, called 

 the cushion, is several cells thick, 

 and the outer part, called the wings, 

 is only one cell in thickness. 



Near the notch of the heart, 

 close to the cushion, several flask- 

 shaped bodies, called arehegonia, are 

 formed. Each archegonium contains 

 an egg cell. Among the rhizoids 

 are the sperm gonads, called anthe- 

 ridia ( ). Many tiny 



motile cells are found in the anthe- 

 ridia at maturity, but as these are 

 discharged and find a small amount 

 of moisture, they reach the egg and 

 fertilize it. 

 It will thus be seen that here, too, as in the mosses, there is an 



alternation of generations, the ordinary fern being the asexual plant 



and the prothallus the sexual. 



Fig. 121. 

 A., a leaflet of the frond viewed from be- 

 low to show the position of the sori. B., de- 

 tails of the sori and veining on a portion of a 

 leaflet. C, section of a sorus; i., indusium; 

 s., sporangia. D., a spore case or sporangium, 

 showing the opening from which the spores 

 (sp.) have been discharged; r., ring. (From 

 Bergen & Davis' "Principles of Botany," by 

 permission of Ginn and Co., Publishers.) 



SPERMATOPHYTES 



This group includes the plants which bear flowers like the rose and 

 lily, as well as such flowerless groups as the pines which have their 

 reproductive organs in cones or clusters, and are by no means so con- 

 spicuous as are those contained in a real flower. 



Two older groupings of these higher plants are : 



Phanerogams ( ). The flowering plants. 



Cryptogams ( ). The non-flowering plants. 



This grouping is one that came into existence before the sexual 

 processes of plants had been studied to any extent, and so is not accurate, 

 because the so-called hidden processes of the cryptogams are in reality 

 more evident than those of the complicated phanerogams. As the seed 

 is the all-important part of a plant from the reproductive point of view, 

 the name spermatophyte has become popular. Seed plants, like ferns, 

 are sporophytes, though there is a gametophyte generation in their life- 

 history, but it is so reduced in structure that it is quite difficult to see. 

 The seed must, therefore, be studied. 



It can readily be understood that the seed, having a hard covering, 

 which is wonderfully adapted for a protective purpose, lends itself well 

 to long vitality, and makes it possible for the embryo to develop so far 



