164 BOTANICAL GAZETTE [February 



figured were often rather incomplete, being only the by-product of 

 another investigation. In several instances the proembryo of other 

 Abietineae has been described as being the same as Pinus, but it is 

 doubtful if all of the investigators verified every step of the embrv- 

 ogeny included in their account. Four tiers of 4 cells (fig. 6) may 

 be produced by several methods of division. 



Lawson (13) describes 4 tiers of 4 cells each for Pseudotsuga, 

 but since this species has no rosette group, the exact order of division 

 and the stages corresponding to figs. 4-7 in Pinus may not be the 

 same. The writer has not had opportunity to examine the pro- 

 embryo or the earliest stages of the embryo in this species, but it 

 may be inferred that one of two things happens in the Pseudotsuga 

 embryo. Either the lowest tier, shown for Pinus in fig. 4^, con- 

 tinues to divide to give rise to the additional two tiers of cells, or, 

 more probably, the exact order of division shown in Pinus is carried 

 out, and it is the rosette tier which elongates. Pinus Banksiana (3) 

 was found with elongated rosette cells in nearly 5 per cent of the 

 cases studied. It is very important, therefore, to know whether 

 the divisions that occur in the proembryo of any species are homolo- 

 gous with those of Pinus. 



Miyake (14), in his study of Picea, includes the stages of the 

 proembryo, and fortunately he figured a stage between fig. 4 and 

 fig. 5, also between fig. 5 and fig. 6, which proves that the rosette 

 tier found in this form is identical in origin with that of Pinus, 

 and the rosettes of these two species are therefore distinctly 

 homologous. 



Tsuga and Abies probably have proembryos identical with 

 Pinus, in view of the results shown for Picea. Only a few stages 

 of the proembryo in Tsuga canadensis are definitely known. These 

 were figured by Murrill (17) as essentially the same as Pinus, 

 but not illustrated in stages older than fig. 3. Abies balsamea was 

 shown by Miyake (15) to be practically the same as Pinus for the 

 stages up to and including fig. 4. In view of the similarity of Pinus 

 and Cedrus in their early embryogeny, there can be little doubt that 

 the proembryo of the latter develops in very much the same manner. 



Only two genera of the Abietineae have not been investigated 

 in some early stage by the writer. These are Keteleeria and Pseud 0- 



