CONIFERALES 3Si 



produce embryos (fig. 339^). They are highly developed in Pinus, 

 where all four of them often produce embryos; so that, with the 

 other four embryos, a single fertilized egg may produce 8 embryos. 

 When three eggs are fertilized, as often happens, 24 embryos may 

 start in a single seed. Since it is possible that six or seven eggs may 

 be fertilized, there couki be 48, or even 56, embryos in a young seed. 

 Rosette embryos are also the rule in Cedrus, but rare in Abies and 

 Tsuga. In the rest of the Abietaceae, except in Pseudotsuga, there 

 are rosette cells, but they do not develop into embryos. 



Rosette embryos are found in Sciadopitys, but not in Taxodium; 

 they are found in Arthrotaxis, but not in Sequoia. The initials for 

 rosette cells may occur in Podocarpus spicatus, and they are found in 

 Cephalotaxus, where they may develop into embryos; but they are 

 not found in Taxus or Torreya. 



Rosette cells sometimes elongate like suspensor cells and function 

 like them. 



CoKER noted that, in Podocarpus coriaceus ,^'^'' a single apical cell, 

 and, later a group of cells, are binucleate. Buchholz found the same 

 condition in Dacrydium cupressinum, and, in a forthcoming paper, 

 has greatly extended the range of forms which show this character 

 to 12 species, so that all members of the Podocarpaceae, except 

 Saxagothea and Microcachrys, probably have binucleate embryonic 

 cells. 



A suspensor, at least in the form of embryonal tubes, characterizes 

 the entire order, and perhaps the entire gymnosperm phylum. The 

 primary suspensor cells, which are well illustrated by the four elon- 

 gating cells of the suspensor tier in Pinus, do not divide. When there 

 are two or more cells in the suspensor, looking as if they had come 

 from transverse divisions in the primary suspensor cells, the addi- 

 tional cells have come from transverse divisions in the lowest tier of 

 cells of the proembryo (fig. 339^ and E). Later, such a secondary 

 suspensor cell may divide periclinally. These secondary suspensor 

 cells have been called "embryonal tubes" and in later embryogeny 

 they may become very numerous. 



In some of his more recent publications Buchholz has made use of 

 the term prosuspensor. This part of the suspensor system seems to 



