TERTILIZATION, DEVELOPMENT, AND FRUCTIFICATION 



prothallium (Fig. 8). This is connected with the soil 

 by hair-like roots. On its lower surface are borne 

 usually both the reproductive organs of the fern, 

 the antheridia, corresponding to the stamens or 

 fertilizing organs of the flower, and the archegonia, 

 performing the office of the flower's pistils, inas- 

 much as their germ-cells receive the fertilizing sub- 

 stance produced by the antheridia. But no seeds 

 are formed as the result of this fertilization. Instead 

 of this seed-formation which we note in the flower- 

 ing plant, the germ-cell in the fern develops into a 

 fern-plant, which forms the " asexual " generation. 



The first fronds of this little plant are very small 

 and simple, quite unlike the later ones. For a time 

 the plant is nourished by the prothallium, but as 

 soon as it is sufficiently developed and vigorous 

 enough to shift for itself, the prothallium dies away, 

 and the fern maintains an independent existence. 



Fig. 9 Fig. io Fig. ii 



First fronds of Maidenhair 



Eventually it produces fronds which bear on their 

 lower surfaces the sporangia containing the minute 

 spores from which spring the prothallia. 



For our present purpose it is enough to say that 

 spores differ from seeds in that they are not the im- 

 mediate result of the interaction of reproductive 



34 



