THE SPOROPHYTE OF SPHAGNUM SUBSECUNDUM 299 
cells usually six or seven in number before walls make their appearance 
in other planes (figs. 1-6). Occasionally, as illustrated by figure 3, the 
basal cell may divide quite early in other than a transverse plane. However, 
the filament of Cells without such irregular divisions is the common occur- 
rence in the material studied at these early stages. 
Fig. II. Embryo of primary segments. Two basal segments show irregular divi- 
sions. Fig. 12. Embryo of 6 primary segments. Basal segment irregularly divided. 
Figs. 13 and 14. Slender types. No irregular divisions in basal segments. All X 300. 
In the later stages of development the writer has been unable to trace 
with any degree of certainty the original wall separating the basal and 
apical cells which Waldner in his drawings shows as sharply defined. As 
illustrated by figures 2-14, it is evident that in the material here studied 
there is no sharp delimitation, hence an exact statement as to the part 
contributed by each of these cells would be unwarranted. While no division 
figures could be found, the elongation of the apical cell as shown in figures 
3, 8, and 12 furnishes strong evidence of apical growth, and finds frequent 
corroboration in the position of the nuclei as illustrated by the two upper- 
most cells in each of figures 7 and 1 1 . Whether this apical growth may be 
supplemented by the occasional intercalary division of a primary segment is 
