1907] _ LAND— EPHEDRA TRIFURCA 283 



Strasburger found one prothallial cell in E. campylopoda and 

 Jaccard none at all in E. helvetica. The technique is difficult and 

 it is not safe to assume the absence of prothallial cells until a very 

 large number of thin sections have been studied. The Gnetales as 

 a group appear to have retained the primitive character of the male 

 gametophyte along with a very high degree of specialization of the 

 female gametophyte. In general a form showing a number of highly 

 specialized characters may be expected to have primitive characters 

 still lingering sorriewhere, perhaps because of the very high speciali- 

 zation of the majority of structures. 



The usual number of sperms or male nuclei in gymnosperms is two. 

 That this reduced number is derived from a gymnospcrm condition 

 in which more than two sperms or male nuclei were produced in a 

 single pollen tube is very probable. The comparative study of anther- 

 idia and archegonia of bryophytes and pteridophytes shows that the 

 antheridium is less conservative than the archegonium. Possibly 

 the retention of the usual two sperms or male cells in gymnosperms 



■ 



is dependent upon the conditions under which they function. In 

 gymnosperms the female gametophyte appears to have two tendencies; 

 first to collect the archegonia into groups — archegonium complexes 

 in a common archegonial chamber; second, to reduce gradually the 

 number of archegonia, maturing the few which are left earlier and 

 earlier in the history of the female gametophyte, until they mature 

 immediately after the free nuclear stage; finally, the free nuclei become 

 eggs. The first-named situation, which perhaps after all may be 

 only one of the stages in the last-named series, is best shown by the 

 Cupressineae; the second tendency is illustrated by the taxad-Gncta- 

 les-angiosperm scries. In Cycadales the sperms in each pollen tube, 

 with one exception as yet, are two and equal, both being discharged 

 into an archegonial chamber in which the archegonia are grouped; 

 and each sperm has an equal chance to function. In Cycadales the 

 archegonia are on the whole numerous, and that the archegonial 

 group has resulted from the coming-together of scattered archegonia 

 and that the tendency is further to eliminate archegonia is shown by 

 the recent studies of Dioon edule by Chamberlain,^ who finds from 



Chamberlain 



Box. 



G.\2ETTE 42:321-358. 1906. 



