20 The Botanical Gazette. (January, i 
at this point, that theinterlocking and interdependence of spo- 
rophyte and gametophyte is such that, wherever they alter- 
nate, certain structures appear, under a rigid classification, to 
be included in both categories. The same cell may be mor- 
phologically sporophytic but physiologically gametophytic, 
or vice versa. This is true of the two unicellular stages 
which serve to distinguish so sharply the higher plants from © 
the higher animals (in which there is but one unicellular stage 
in the life-history of the organism). The spore, since it is 
structurally part of the sporophyte, must be grouped by mor- 
phology with the other sporophytic structures. But, since 
the spore is also the first stage of the gametophyte which be- 
comes elaborated through development, it must, by the clas- _ 
sification of physiology, be grouped with the gametophyte. 
The same paradox is to be noted for the fecundated egg. It 
is quite as distinctly gametophytic from a morphological 
point of view, but in the physiological sense it is sporophytic. — 
A consideration of the gametophyte of the Muscinez re-_ 
veals to the ‘student its comparatively high structural rank ~ 
among gametophytes. This high rank is evidenced most pat- — 
ticularly by its developing not as a continuous structure with | 
but one developmental stage, but as a discontinuous 
structure with two distinct developmental stages. While | 
; 
i 
gametophytes above and below the Muscinee may be 
considered as generally monomorphic, the gametophyte 
of the Muscinee is very constantly dimorphic. It ap- 
pears in two readily separable stages of certainly deep 
phylogenetic meaning. The first of these stages iS 
being particularly evidenced by increase of propagative 
with perfecting of propagative apparatus. The proto 
