i 



1907] LAND— EPHEDRA TRIFURCA 289 



mod 



great 



SUMMARY 



Ephedra trijurca is monosporangiate, but occasionally bisporangiate 

 strobili occur. 



The beginning of the staminate and ovulate strobili can be seen 

 in December; the pollen is shed about April i, and the ovulate strobili 

 early in May. 



The anthers, developing in acropetal succession on a compound 



strobilus, are surrounded by a perianth. 



Two integumentSj free from each other except at the base of the 



ovule, are present; the outer has four rudimentary bundles, the inner 

 two. 



The nucellus is free from the inner integument for more than half 

 its length, 



A conspicuous pollen chamber reaches down and lays bare the tip 

 of the gametophyte, on which many of the pollen grains come to rest. 



The pollen chamber is finally closed by a plug derived from the 

 outermost layer of the gametophyte cells forming the bottom of the 

 chamber; this plug prevents the escape of the embryo into the pollen 

 chamber. 



gram 



poll 



before the pollen tube appears. 



Two male nuclei equal in volume and optical appearance are pro- 

 duced. 



posed 



antipodal 



rial cells at the base. A column of thin-walled cells containing much 

 food extends from the base of the archegonia through the center of 

 the gametophyte nearly to the haustorial region, marking out the line 

 the embryo will follow. 



Fertilization is possible within ten hours after pollination. 



The walls of the jacket cells break down about the time of fertiliza- 

 tion and their contents mingle with the cytoplasm of the egg; occasion- 

 ally some of the jacket cells closely resemble the egg. 



