322 BOTANICAL GAZETTE [MAY 
hemisphere, was an immediate consequence of the two condi- 
tions already mentioned, viz., transverse segmentation and periph- 
eral position of the archegones. The persistence of the function 
of sporogeny in the epibasal hemisphere cell-descendants, and 
the disappearance of this function from the hypobasal tract is 
a most natural division of labor, and in each area improvements 
for reproduction and for absorption have been steadily evolved. 
By the relations of the young embryo to the parent prothallium 
and by the ancestral relations, orientation is determined. This 
is an adaptive phenomenon. 
Kienitz-Gerloff%° in a general article suggests, without having 
considered, however, a very full series of forms, that torsions 
(Drehung) may explain the oblique position of the Pteris epi 
basal segment as compared with that of the mosses, seeming to 
propose a spontaneous shifting of the plane of segmentation. 
This explanation I am unable to accept for the whole group of 
positions seems to be clearly adaptive. In the paper cited, 
Kienitz-Gerloff gives four diagrammatic longitudinal optical sec: 
tions of embryos illustrating his idea of lateral torsion. This 
paper is of interest also from its ingenious though faulty deter- 
minations of homologies between Bryophyta and Spermatophy' 
in quite the manner of the older school of embryologists. 
SUMMARY. 
1. The orientation of the plant-egg is at bottom a phenoit 
enon of adaptation. facts of 
2. The conception of a basal wall is founded ral 
phylogeny so profound that it is necessary to ee n log- 
as basal which separates morphologically distal from morP cous 
ically proximal regions. The first wall formed O8y * 
not be the basal wall. 
3. Three principal types of egg-orientatio ‘cet 
the primitive or bryophytic, characteristic also of Equis : 
Angiopteris ; the semi-inverted, characteristic of Isoetes @ 
sskryptosam™ 
n are recognized: 
m an 
: f 
® Ueber den genetischen Zusammenhang der Moose mit den Ge 
und Phanerogamen. Bot. Zeit. 34: 705. 1876. 
