Polyembryony. 177 



POLYEMBRYONY. 

 By D. P. Pbnhallow, B.Sc. 



According to Strasburger, 1 poly embryo ay, as it occurs in 

 Funkia, Allium, Nothoscordum, oranges, &c, arises from adven- 

 titious outgrowths, which, originating in the nucleus exter- 

 nal to the embryo-sac, ultimately penetrate the latter and 

 then form true embryos, although independently of fecunda- 

 tion. They therefore represent, according to Gray, instances 

 of true parthenogenesis. More recently, G-uignard 2 has 

 shown that polyembryony is not uncommon in the 

 Mimosea? ; while B. Jonossn 3 points out a similar case in 

 Trifolium pratense, which he ascribes to the development 

 of several ovum cells in the same embryo-sac. 



Although the common occui*rence of polyembryony in 

 oranges is well known, a very interesting instance of its 

 frequency in certain varieties was recently brought to notice. 

 Among several hundred seeds planted, it was observed that 

 in the Florida oranges of the more common sorts, and the 

 ordinary Spanish oranges, polyembryony was comparatively 

 of little frequency, but in the Tangierine, its occurrence was 

 most marked. In transplanting some young trees on the 

 26th of April, then about three weeks old, opportunity was 

 taken to note the number of plants to each seed. Of all 

 those examined, only six were found to have produced a single 

 plant, while all the others had produced from three to four 

 plants each. The following is a summary of the results 

 obtained : — 



Whole number of Seeds » 38 



Seeds producing one plant 6 = 15.8 p. c. 



" " two plants 19 = 50 " 



" •' three " 9 = 23.7" 



four " 4 = 10.5" 



1 Am. Jour, of Science, 1879. xvii, 334. 



2 BulL Soc. Bot., 1881. xxviii. 177. 



3 Bot. Notiaer, 1883. 135. 



