230 THE ANATOMY OF WOODY PLANTS 



closed reproductive leaf or megasporophyll, and later enter the ovule, 

 either through the micropyle (in porogamous forms) or through 

 the chalaza or breech of the seed (a condition found in the so-called 

 chalazogamous dicotyledons). Not only do inclosure of the ovules 



FIG. 170. Diagram of a poroga- FIG. 171. Diagram of a chalazog- 



mous dicotyledon. amous dicotyledon. 



in an ovary and the consequent exclusion of the pollen from direct 

 access distinguish the angiospermous seed from that found in 

 lower forms, but likewise the very considerable reduction in the 

 amount of gametophytic tissue. In this large group of seed plants 

 the prothallial portion of the young seed contains typically eight 



