19 2o] BUCHHOLZ—POLYEM BRYONY 157 



examined 



at least occasionally, the usual separation into 4 primary embryos 

 did not occur, but hundreds of embryos dissected out in slightly 

 later stages (several days older) of material from the same source 

 failed to reveal even one case without the usual cleavage poly- 

 embryony. 



mbryos 



In many 



cases they have suspensors which elongate distinctly, and were 

 it not for the fact that the dissections clearly show their relation to 

 the basal plate (bp) , these rosette embryos would in some instances 

 very easily be confused with the primary embryos. On the whole, 

 the embryos of P. Laricio furnish probably the most satisfactory 

 type for use in laboratory instruction, both on account of their 

 clearness in displaying the rosette embryos, and their large size, 

 which makes them easier to dissect. 



Abietineae. — The other genera of Abietineae that were dis- 

 sected and examined are Cedrns libani, Tsuga canadensis, Abies 



<p> 



taxifolia 



Abietineae 



Method and material.— The technique was that of dissection 

 described in detail in the writer's work on Pinus. No modifica- 

 tions of these methods were found necessary, but perhaps it should 

 be repeated that the living material is indispensable for some species. 

 A study of preserved material is possible, but it is not so satisfactory. 

 The embryos may be killed and preserved indefinitely, however, 

 after they have been removed by the methods described. The 

 proem bryo stages must be studied by the well known methods for 

 making serial sections. The writer is indebted to the following 

 for the material used during the summer of 191 7 : W. G. Waterman 

 for material of Abies and Tsuga from Frankfort, Michigan; S. D. 

 Magers for collections of Abies balsamea and Picea mariana from 

 Marquette, Michigan; D. Hill Nursery Company, of Dundee. 

 Illinois, for material of Pseudotsuga, Larix, and Tsuga canadensis, 

 collected on their grounds. Very satisfactory material of Pseudo- 

 tsuga taxifolia was supplied by the Friday Harbor Marine Station 

 of Puget Sound. During June and July C. T. Hilmers supplied 



