452 BOTANICAL GAZETTE [December 



aspect as the nuclei in vegetative filaments. In figs. 35 and 36 are 

 given anaphase and prophase of the vegetative division. Until 

 about the 4 or 5-celled stage the young gametangium consists of a 

 single row of cells, after which division also occurs perpendicular 

 (figs. 37, 48) to the direction of the axis of the gametangium, so that 

 there are two rows of cells. When the young gametangium has 

 reached the 8 or more-celled stage and consists of two rows of cells, 

 the nucleus in both the resting and dividing condition has neces- 

 sarily been forced to assume a somewhat irregular form so as to 

 occupy the largest possible space, and it does not decrease much in 

 size in spite of the multiplied divisions and consequent diminution 

 of the cells of the gametangium (figs. 40, 41). 



Another division perpendicular to the direction of the growth 

 of the gametangium occurs (figs. 42, 44), and the gametangium 

 becomes a structure composed of four rows of cells. The diminu- 

 tion in the size of the nucleus is now recognizable (figs. 43, 4S)- 

 Although the chromosomes which appear in prophase are 24 in 

 number, their size has become remarkably reduced to about half 

 the diameter of those appearing in earlier mitoses. The diminution 

 may proceed still further during the divisions which multiply the 

 number of the cells in a tier. There now occurs the third and last 

 division perpendicular to the axis of growth of the gametangium 

 (fig. 50), resulting in a structure 



com 



gametanrium shows eierht rows of cells, a number 



mitoses may occur that increase the numb 



(figs. 46, 47, 48, 49), and during these mitoses there are always 

 24 chromosomes. These longitudinal divisions of the game- 

 tangium, as well as the transverse, are strictly simultaneous, but 

 they proceed at a nearly uniform rate, so that ultimately there is 

 formed the well known male gametangium of Cutleria, which is 

 composed of eight rows of cells, each row made up of a varying 

 number of cells. The number of cells in a row may be even more 

 than 24, the cells of each row lying side by side with the cells of the 



contiguous 



gametangi 



male gamete mother cell, within which a single male gamete 

 formed. 



The mother cell contains a sino-le Irtw nucleus situated in t 



