158 BOTANICAL GAZETTE [February 



weekly collections of the material growing on the University Farm 

 near Lincoln, Nebraska, as follows: Picea excelsa, Psendotsaga 

 taxifolia, Pinus ponderosa, P. sylvestris, P. Laricio, and P. Strobus. 

 In addition to this, the writer made many trips to various places in 

 the vicinity of Chicago to secure material of some of these same 

 species. During the summer of 19 18, W. W. Robbixs supplied 

 a collection of Pseudotsuga taxifolia from near Fort Collins, Colo- 

 rado, and arranged for a collection of Pinus cdule from Cortez, 

 Colorado; and E. J. Kraus made several collections of the cones 

 of Cedrus libani from the grounds of the Oregon Agricultural College, 

 Corvallis, which reached the writer in excellent condition. 



Cedrus has almost the same early embryogeny as Pinus. The 

 primary embryos, however, do not separate until some time after 

 the suspensor cells and first embryonal tubes have both elongated, 

 and therefore cling together very much longer than in any species 

 of Pinus that was investigated. In all the slightly older stages 

 the embryo units had separated, indicating that cleavage poly- 

 embryony is likewise a constant feature in Cedrus. An apical 

 cell stage seems to exist in this genus, and rosette embryos usually 

 occur, somewhat less developed than in the average pine. The 

 older suspensor cells collapse soon after separation of the primary 

 embryo units. 



Tsuga canadensis also resembles Pinus very much in its embry- 

 ogeny. In this species the embryo units separate into the 4 primary 

 embryos, yet they cling together longer than in any pine, apparently 

 about as long as in Cedrus. Cleavage polyembryony occurs regu- 

 larly. This conclusion is based upon the careful dissection and 

 examination of the embryos of about 40 ovules of a more advanced 

 stage, among which no exceptions were found. 



Save for their difference in size, Tsuga, Cedrus, and Pinus appear 

 very similar in the first stages of suspensor formation. In Tsuga, 

 however, the rosette cells are very ephemeral; they were not found 

 to divide before the collapse and disintegration of their contents, 

 apparently giving no rosette embryos. The suspensor cells also 

 collapse very soon in Tsuga, leaving only a shred of tissue which 

 connects the shriveled rosette to the embryo system below. As in 

 Pinus, the early embryos develop by means of an apical cell. 



