148 MORPHOLOGY AND LIFE HISTORY 



2. State, with reasons, whether you would considei 

 Puccima graminis higher or lower in the scale of 

 life than Vaucheria (or Fucus), and Albugo (or 

 Mucor) . 



3. Write a brief summary of the life history oi Puccima 

 graminis, and devise a diagram to illustrate this. 



NOTE 



From the fern to the wheat rust we have studied plants 

 in the descending order, from higher to lower in the scale. 



We now return to the ferns, taking the quill-wort 

 (Isoetes), illustrating the Eusporangiatae. 



The systematic relationship of the Isoetaceae is doubt- 

 ful. On the basis of certain structural features of the 

 gametophyte (e.g., the structure of the archegonia, and 

 the possession of multiciliate sperms), some botanists 

 class them with the Pteridophyta. On the other hand, 

 some features of the anatomy of the sporophyte (e.g., the 

 possession of a ligule on the sporophyll) suggests that 

 they are more closely related to Selaginella (Lepido- 

 phyta). 



