210 SYMMETRY OF THE SPOROPHYTE 
construction, though possibly dorsiventrality may have existed among the 
smaller forms. Of modern Lycopods, the mature, shoots of Lycopodium 
show in relation to their position the most gradual transitions from the 
radial to the dorsiventral. The species of the sub-genus Se/ago, and 
Sub-Selago maintain the radial construction, and are for the most part of 
upright habit. The rest of the genus is very variable: the shoot is some- 
times radial, as in Z. zzundatum: or distinctly distichous forms may occur, 
such as L. Phiegmaria and xummularifolium, which are both pendulous 
Fic. 105. 
A, young sporophyte of Danaca simplicifolia still attached to the gametophyte, pr. 
x3. 8, an older sporophyte of the same species. C, gametophyte of A ugiosteris evecta 
wep yous, sporophyte. (A, B, after Brebner; C, after Farmer, from Campbell’s- Wosses 
and Ferns. 5 
epiphytes. The change from the radial type may be apparent first in a 
slight inequality of direction of the leaves, otherwise equal, as in the 
creeping shoots of Z. annotinum or clavatum: or in the marked inequality 
of their size and structure, as in Z. complanatum or alpinum. Goebel 
has shown! by experiment on Z. complanatum that the dorsiventrality 
is directly induced by light. Finally, the climbing species, Z. voludbzle, 
is specially characterised by a distichous form of the shoot not unlike 
that usual in Selagznella. It has already been concluded on other 
grounds that the Seago type of Lycopodium is the most primitive: it 
is this same type which retains most constantly that radial construction 
which there is reason to believe is a primitive character. 
1 Organography, vol. i., p. 252. 
