102 MORPHOLOGY OF SPERMATOPHYTES 



scribed a most interesting modification in the formation of the 

 proembryo in Cephalotaxus. The egg nucleus " divides three 

 or four times," which means the production of eight or sixteen 

 free nuclei. These nuclei pass to the bottom of the oospore and 

 divide further, giving rise to " a number " of free cells, which 

 organize tiers " as in Taxus." Just how these numeroiis free 

 cells organize the tiers the author does not state, and his figures 

 indicate that the condition of his preparations would forbid any 

 claim beyond the mere existence of tiers. The number of free 

 nuclei and cells, however, before the organization of tissue, is 

 the important point, and indicates what would seem to be the 

 most primitive embryogeny among the Conifers. Although 

 normally in Pinus an embryo is developed at the end of each 

 suspensor cell — that is, a single oospore gives rise to four em- 

 bryos — ^we found in P. Laricio cases of a single embryo develop- 

 ing from the plate of four cells carried down by the four sus- 

 pensors. It seems that this is the normal behavior in Picea 

 excelsa, in which the suspensors remain coherent, forming a 

 single compound suspensor at the end of which a single embryo 

 develops. So far as the records go, the development of a single 

 embryo from the embryonal plate seems to be true in all groups 

 excepting Abieteae. Among the Cupresseae it is reported that 

 each of the three tiers of the proembryo is originally a single cell, 

 either remaining so, as in Cupressus, or dividing, with the ex- 

 ception of the embryonal cell, as in Thuja, or all dividing, as 

 in Juniperus. If this sequence of events be true, it would seem 

 to follow that in these cases the fusion nucleus passes to the 

 bottom of the oospore without division, and there behaves in 

 building up tiers just as do the four basal nuclei in the case of 

 Pinus. Such statements, however, need further investigation. 

 The number of cells in each tier may also vary from four, the 

 usual number in Taxus being six, and sometimes reaching 

 even ten. 



2. Development of Suspensor. — The suspensor, or rather the 

 four suspensors, are formed by the remarkable elongation of the 

 cells which form the middle tier (Fig. 76, H). The lowest tier 

 is thus carried down into the midst of the endosperm, and the 

 uppermost tier remains in the base of the oospore, forming the 

 so-called "rosette" of Schacht. The suspensors become long 

 and tortuous (Fig. 78, A), and each bears at its tip one of the 



