ths] ORIENTATION OF THE PLANT EGG 321 
_ fe of the thallus where interference of closely packed branches 
wilnot hinder the egg-seeking, locomotive movements of the 
ems. Together with this definite peripheral location of the 
swual cells arises the need for protection of them from injurious 
_ impacts of all sorts and sharp bristling chet are developed. 
In many Hepaticze by invagination, and in Musci by envelop- 
mat with bracts, the sexual organs are protected, and the 
siposure due to their morphologically peripheral position is modi- 
fed or almost completely negatived. In Anthoceros the pro- 
| lective instinct results in the habit of developing the spermaries 
_ ‘Mactually closed cavities, not to be opened until the sperms 
‘equite mature. Such derived positions while adaptational in 
- tietruest sense must be admitted to have important effects upon 
the reproductive rank of the organs or organisms in question. 
Primitive reactions of segmenting eggs to their environment.—The 
st necessity that confronts a plant egg is that its position be 
““lastoinsure fecundation. That this may take place it is 
“essary that the egg should be protected against harmful 
~ itluences, but should be exposed to the ingress of the sperm. 
After fecundation it is necessary that the embryo should be pro- 
ted and nourished and that it should, with the least waste of 
oly . energy, develop into a functional sporophyte. The 
Share . a sporophyte may be briefly defined as the awe 
+ Under ag many end as certainly germinable spores as possib ‘ 
“ith such povrasities the eggs are at first peripherally dispose 
S Protective layers about them as may have been 
ig snd maintain this general position until spermatozoid- 
wc 'on is abandoned, passing over through the Ginkgoales 
E Yeadales to pollen-tube fecundation. 
..* Pfimitive segmentation-types as seen in Riccia may have 
: a under direct stimulus by the force of gravity, as a 
aie but very early the direction of the basal wa 
Ong a with reference to the archegone axis and age 
ee anly in course of extended wiaeeaistss : i 
 Ugints aay specialization of the archetypal embryos, Dring ' 
oe €nce an epibasal as distinguished from a hypobasa 
