124 BOTANICAL GAZETTE [AUGUST 
STRASBURGER (12) states that the starch soon disappears from the 
megaspore mother cells of T. baccata, but COKER (g) in his figures 
shows starch grains in the megaspores as well as in the megaspore 
mother cells. The starch is not confined to the megaspore region, 
but is found abundantly in the adjoining cells, and some of it occurs 
throughout a considerable portion of the nucellus in T. canadensis. 
The method of formation of a tapetum about the megaspore 
mother cells, as pointed out by STRASBURGER (12) in T. baccata, 
also holds for T. canadensis. ‘These cells are formed more or less 
obliquely to the long axis of the megaspore cells (fig. 34), are rich in 
content, and stain differently from the megaspore mother cells. 
THOMSON (15) speaks of the tapetum derived from the nucellus 
as a “secondary tapetum,” in distinction from forms in which the 
tapetum is derived from the sporogenous tissue, in which case it is 
called a ‘‘primary tapetum.” GOEBEL pointed out long ago, how- 
ever, that the significance of the “‘tapetum”’ is physiological, and not 
morphological, and that it may have a variety of origins. The 
megaspore mother cell seems to be the usual winter condition. 
_ While SrrAsBURGER (12) says the megaspore mother cells of 
T. baccata are completed in October and that further development 
takes place the next spring, this does not always hold for T. cana- 
densis, as I have found young female gametophytes of several free 
nuclei in some of the material collected in November, 1913. Most 
of the ovules taken at this time showed the mother cell condition, 
but even in some of the ovules collected as late as December it 
‘may be doubted whether the megaspore mother cells had become 
fully matured. Evidently, therefore, the time for the maturity of 
the megaspore mother cells and the formation of megaspores may © | 
__-vary, yet the general statement may be made that the mother 
oh ie the usual winter condition and that megaspore formation _ 
me - bani de takes ~ in the pone with the renewal of the growing = 
