268 



MORPHOLOG V. 



the archegonia. r)nt' of them in longisertion is shown in fig. 

 308. It is tlaslc-shaped, and the broader portion is sunk in the 



Fig. 309. 

 Mature and open archegonium of fern {Adiantuni cuneatum) witli spermatozoids making 

 their way down tiirougti tile slime to the egg. 



tissue of the prothallium. The egg is in the larger part. The 

 spermatozoids when they are swimming 

 around over the under surfaee of tlie pro- 

 thallium come near the neck, and here they 

 are caught in the viscid substance which 

 has oozed out of the canal of the arche- 

 gonium. From here they slowdy swim 

 down the canal, and finally one sinks into 

 the egg, fuses with the nucleus of the latter. 

 and the egg is then fertilized. It is no'\- 

 ready to grow and develop into the ten 

 plant. This brings us back to the spor' 1 



phyte, which begins with the fertilized egg. 



Fig. 3to. 



Fertilization in a fern 

 'Marattia). .v/, sperniato- 

 zoid fusing with the nu- 

 cleus of the egg. (After 

 Campbell. I 



Sporophyte. 



668. Embryo. — The egg first divides into iwn cells as shown in fig. 228, then 

 into four. Mow lr(.)m each one of these (|iian(h-ants of the embryo a definite 

 part of the plant develops, from one the lirst leaf, from one the stem, from 

 one tlie root, and from the other the organ wliieh is called the foot, and which 



