i808] ORIENTATION OF THE PLANT EGG 319 
must have early begun the development of an adventitious 
“foot” and root. 
PHANEROGAMIC ORIENTATION AND SEGMENTATION TYPES. 
All segmentation types among flowering plants, with the 
wssible exception of that manifested by the extraordinary plant 
Ginkgo biloba, are referable to class C.. Various secondary 
_ tologic modifications have arisen, the most remarkable being 
he meroblastic segmentation in Conifer, the free-nuclear seg- 
mentation in the Gnetales—a phenomenon ecologically compar- 
ible to the free-nuclear origin of female prothallial tissues in 
Selaginella or to endosperm origin in most seed-plants — and the 
eduction of the suspensor, as in Pistia, Listera, Cypripedium, 
the Mimoseze and Hedysaree among others. It is not possible, 
towever, to name any suspensorless flowering plant embryo 
“cept that of Ginkgo biloba, in which the absence of suspensor 
pot plainly and unmistakably a secondary adaptation. In 
Ginkgo alone is there a suggestion that the embryogeny belongs 
the general fern type rather than to the lycopodineous. 
Other well-known old and new facts about Ginkgo should be 
“tsidered in this connection but will here be passed over with- 
‘ut further notice. 
GENERAL CONSIDERATIONS. 
wa tive phenomena in reproductive warts Ung 2 
aaa organs of the plant, those concerned with rep 
_ “t€ more or less exactly adapted to their environmes™ 
es me they are less plastic than the organs of the vegetative 
‘and hence do not show the epharmonic characters so vari- 
a stem, root, and leaf structures may. For this reason they 
my : — universally, by modern as by ancient taxonomists, 
: "ployed as the landmarks of phylogeny, not easily shifted by 
' ad outward influence. Yet form and structure “ a 
e Y connected with their special functions may be cca 
on then are assigned 
and developed inthem. Special positions 
ti i z j i: 
—  *nder outward stimulus, and their structure, shape, 512°, 
