T907] CALDWELL-^MICROCYCAS CA LOCOMA 135 



{fig. 33), but usually they are even with the surface, as shown 

 in the case of the single neck cell in fig. 34. In some cases at least, 

 the neck cells break down, leaving the central cell exposed at the 

 surface of the gametophytc {figs. 55, 36). The contents of the 

 archegonia showed considerable variation. In such archegonia as 

 are shown in figs. 33 and 34, there is the usual condition in which the 

 ventral canal cell has not yet been cut off; in numerous other cases, 

 however, two or three nuclei were found (figs. 36, j/, jp). Coker 



(11) found that in Taxodium the free ventral canal nucleus after 

 fertilization divides amitotically ; and in Podocarpus he observed 



(12) the same phenomenon. It is possible that 

 some of the nuclei found in the archegonium of 

 Microcycas may have arisen in this way, but failure 





Fig. 13. — An old 



staminate cone. 



to find any ventral canal nuclei in the usual position, 



though many central cells were examined, indicates 



that the material was not old enough to have formed 



ventral canal cells. That some of the central cells 



were almost ready to divide, hower, is shown by 



the condition of the nuclei in figs. 34 and 3j. It 



is probable that archegonia may unite by the 



absorption of their dividing walls, for they often 



crowd upon one another very closely, as in fig. 38, in 



which absorbtion of the separating walls would 



result in just such a condition as is shown in figs. 36 y 



3'/y and jp. Comparison with other cycads would 



also suggest that the archegonium has not reached the stage for 



cutting off the ventral canal nucleus. It seems altogether probable 



that a ventral canal nucleus is cut off subsequently, and that the 



two or more free nuclei observed are the result of the union of two 



or more archegonia. 



The development of jacket cells, as described Ijy Gorosciiaxkin 

 (i3;,Treub (14), Ikexo (7), Smith (15), Stopes and FL'jn (16}, 

 is much less regular in Microcycas than in the other cycads studied. 

 This is probably due to the crowding together of archegonia and the 

 consequent absorption of intervening tissue. 



The ver}- large number of archegonia and their peculiar distribu- 

 tion are suggestive of primitive conditions, and this is emphasized 

 by association with the large number of sperms. 



