1 24 MAIDEN-HAIR, FERN. 



i. The number of rows of cells composing the 

 neck. 



ii. The canal between the cells of the neck, and 

 extending from its apex to the imbedded 

 portion of the archegonium. This canal is 

 difficult to distinguish unless it contains a 

 granular substance. 



iii. The cluster of cells at the base of the neck 

 imbedded in the prothallium, the body of the 

 archegonium. 



iv. At the inner end (base) of the canal, in the 

 midst of the cells of the body, a single large 

 central cell, filled with a rounded mass of pro- 

 toplasm, the oosphere. 



v. Draw the archegonium. 



ANNOTATIONS. 



Regarding only the position of organs, perhaps the 

 most striking difference between Adiantum and Atri- 

 chum is to be found in the fact that the former has its 

 leaves only above the ground, while the real stem is 

 buried below it. In contrast with those low plants 

 whose rhizoids have served them well enough for hold- 

 fasts, the fern has developed strong fibrous roots which 

 ramify widely and perform this office, assisted by the 

 buried stem. These roots are made necessary not 

 only by its greater stature and the consequently greater 

 strains, but by the necessity of wider foraging for the 

 supply of food. The roots must push their way 

 among the particles of soil, and, to protect the tender 

 tissues of the growing point, the tip of the root is 

 covered by a cap of cells, which arise from segments 

 cut off from the outer face of the tetrahedral apical cell. 



