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1904] DAVIS—SEXUAL ORGANS IN PLANTS 253 
In this distinction of protoplasmic behavior during sporogenesis 
and gametogenesis (7. e., the formation of cell walls during the seg- 
mentation of the protoplasm) lie the fundamental peculiarities of 
the sporangium and gametangium. And in this distinction are based 
my views of the homologies and origin of these structures. Associated 
with the peculiarity is the fact that sporangia and gametangia are 
almost universally superficial, and perhaps always have their origin 
from superficial cells. There may be exceptions to this general rule, 
as the antheridia of Anthoceros and some sunken sexual organs of 
the Lycopodineae, but these have not been sufficiently studied to 
justify conclusions. Thus, Emma Lampa (703) has obtained Antho- 
ceros plants bearing antheridia of superficial origin, and regards 
these as Tepresenting primitive conditions, and one cannot guess 
what investigations among the pteridophytes may bring forth. The 
teasons for the superficial position of reproductive organs are probably 
at bottom physiological, although of course one may readily advance 
teleological explanations. 
: I do not find the same difficulty as Miss Lyon in deriving the gener- 
alized and sunken sexual organs of some pteridophytes, notably the 
Lycopodineae, from superficial structures. Of course one does not 
relate them to extreme emergent types, such as are found in the 
Jungermanniales and Marchantiales. But a simple type of arche- 
penitim, Sessile upon the gametophyte, might incorporate adjacent 
oe 8 structure, especially if these are so generalized in char- 
Ha A ave reproductive potentialities, and thus become a more 
thither ee oa The msnepeney of an archegonium depends 
a on coy ng out of a superficial cell, from which, so far as 
“pe if St heck region is derived as from a growing point. And 
a pales archegonia unquestionably takes its position 
ical J — cells develop an uplifted portion of the gametophyte 
nie metangia which are deeply sunken in the gametophyte, 
Yeopodium (and few have been reported), are perhaps as 
‘xtreme in the direction of . ‘ ae 
Mosse ae ar i (9) suppression as are the gametangia oO 
o lverworts in the direction of emergence. These 
ioe ‘St ie present difficulties that demand special 
of the iia oly oe Orem, Thus, there may be an evolution 
gametangium in both directions, on the one hand 
