June 1891.] BOTANICAL SOCIETY OF EDINBURGH. 139 



conopsea, &c., three cells are formed ; while in Allium 

 fistulosum the archesporium gives rise to only two cells, the 

 lower of which developes into the embryo-sac. 



If then the embryo-sac was the equivalent of two spores, 

 and if the archesporium corresponded to a sporocyte, as Ward 

 believes, we would have to consider a sporocyte capable of 

 giving rise to a number of spores, varying from seven in 

 number, as in Bosa, down to three in number, as in 

 Allium ; this does not seem, however, to be in accordance 

 with spore- formation, as it takes place in Cryptogams and 

 in the formation of pollen-grains. 



As the initial cell, called the archesporium or embryo-sac- 

 mother-cell, gives rise to a row of cells varying in number 

 from two to seven, it is evident that we cannot regard the 

 cells derived from it as spores, nor it itself a sporocyte, it 

 must be therefore either a special-spore-mother-cell or a true 

 archesporium. In either case tissue derived from it is sporo- 

 genous tissue, which will at one time develope into sporocytes, 

 and these into spores. 



Let us study how the row of cells is formed in Myosurus, 

 and what the fate of each cell is. The archesporium divides 

 into two cells, separated by a very distinct, sharply-defined 

 wall. Each of the two newly-formed cells may repeat the divi- 

 sion, although as a rule only the lower cell does so ; we see 

 a struggle has commenced, the lower cell is better fed than 

 its sister-cell, as it lies in close contact with the plerome- 

 elements of the ovule. The wall formed across the lower 

 cell is as sharply defined, but narrower than the primary 

 wall running across the archesporium. We have seen how 

 that daughter-cell of the archesporium which lies next the 

 plerome-elements is the more vigorous one, and we shall see 

 that of the two cells derived from it, the one next the 

 plerome-element is again the more vigorous, for the latter 

 will be the future embryo-sac. 



At this time the walls of all the cells in the row undergo 

 gelatinisation, with exception of the two walls mentioned 

 above. If the archesporium has divided into three cells, 

 two long lines parallel to the long axis of the ovule, joined 



by two short crossbars, j^j, deeply stained with Kleinen- 



berg's hasmatoxylin, No. 1, are seen on microscopical 



