4 18] ORIENTATION OF THE PLANT EGG 399 
hdebeck** gave a full account of the Equisetum embryogeny 
1878, and his figures serve to illuminate all the important , 
sages. The basal wall divides the egg into a distal half as 
istinguished from a proximal. The distal or epibasal hemi- 
“at develops into the shoot tract, while the proximal retains 
-isancestral character of a foot from which, however, the root 
springs endogenously (fig. 5). It may be regarded, I think, 
that the type of embryogeny shown by 
‘quisetum is the most primitive among 
fietidophytes, and indicates the probable 
phylogenetic significance of the root as 
embryonic organ of Pteridophyta. The : 
Toot is developed as an emergence from 
Bee tion- path of the nursing foot. 
i se the vegetable kingdom it “moconueec sees e = 
sce universally arises from internal Fic. 5.—Embryo of 
of the and may be regarded asa branch gs ar 
the h stele. The precise behavior of 
gage hemisphere of Equisetum, which enlarges by 
8 2nd growth into a bulbous body and then devel- 
aut from an apical cell, not superficial, may be taken fora 
f the s pyon of the original evolution of the root as an organ 
em ee Ptyte. In this sense root is not homologous with 
| thegoni % indeed, a new structure. It seems to be, for the 
] tive tract = hg of plants, essentially first of all an glee 
Sttoundin Nd it comes into existence through adaptation ee : 
- latger . of the sporophyte endowed with a imcigaihe* 
: distinction Osynthetic area. This conception 1s 1n direct - ra 
Baerel to an older view, that root as a morphologica — 
y the proximal end of the axis, and that its primitive 
Action i 
Was support rather than absorption. 
e of the early 
E 
mbryogeny of Angiopteris —Our knowledg 
hyte is due 
po the development of the Angiopteris sporop 
hg, Mwickelung des Keimes der Schachtelhalme. Jahrb. Wiss. Bot. 11 #575: 
