4 S BOTANICAL GAZETTE [july 



dra, in which it has been described by Land. 6 The development 

 of the tetrad was observed ; and although the early anaphase of the 

 first mitosis was not available for the counting of chromosomes, the 

 late prophase of this mitosis and the anaphase of the second mitosis 

 showed clearly that the chromosome numbers are 12 and 24. 



SUMMARY 



1. The "antipodal tissue" described by Lotsy as occurring. in 

 Gneium Gnemon at the fertilization stage is a sharply differentiated 

 nutritive tissue developed in the nucellus beneath the embryo sac, 

 which at this stage contains only free nuclei, as described for other 

 species of Gnetum. 



2. Embryo formation begins with an excessive, suspensor-like 

 elongation of the fertilized egg, accompanied by free nuclear division 

 and cleavage walls; and the continuation of free nuclear divisions 

 and cleavage walls in the embryonal cell until a multicellular embryo 

 is formed. 



3. The endosperm encroaches upon the tissue of the nucellar 

 beak with some irregularity, an irregularity which reaches its extreme 

 expression in Torreya, with its so-called "ruminated" seeds. 



4. The inner integument of the ovule is the morphological equiva- 

 lent of the "inner fleshy layer" of the single integument of other 

 gymnosperms; and the occurrence of two sets of vascular strands 

 is a relatively primitive condition, which has been departed from 

 by Ginkgoales and Coniferales. 



5. The chromosome numbers are 12 and 24. 

 The University of Chicago 



EXPLANATION OF PLATE VII 



Fig. i.— Embryo sac at an early stage, with centrally placed group of eight 

 free nuclei; the cell above, with a large nucleus, is another embryo sac. X500. 



Fig. 2.— Somewhat later stage of embryo sac (all the nuclei not included), 

 showing the beginning of the formation of the pavement tissue; a second embryo 

 sac is also shown. X500. 



Fig. 2a. — An ovule at an early stage, showing the two integuments and the 

 relation of the pavement tissue and embryo sac to the nucellus at the stage shown 

 in Jig. 2. X4°- 



6 Land, W. J. G., Spermatogenesis and oogenesis in Ephedra trijurca. Bot. 

 Gazette 38:1-18. pis. 1-5. 1904. 



