EMBRYOLOGY 357 
with the mode of development of these parts in mature plants. For 
the variability in haustorial development within the genus the study of 
the embryology of Zycopodium has already prepared the way. Both genera 
demonstrate the inconstancy of the haustorial organs of the embryo, and 
justify my conclusion of more than twenty years ago, that these swellings 
FiG. 190. 
Embryos of Selaginella spinulosa. A-D illustrate the segmentation. I. I., first wall, 
separating the suspensor; IV. IV., corresponds to wall similarly marked in Figs. 183, 186, 
and:to wall 4, 6 in Fig. 182; 2=wall marking off the vascular strand of the axis. 
&, Ko=cotyledons; L=ligule; W=root. A=section of germinated spore with embryo 
in sith. G, H=seedlings. H, natural size; G, enlarged. /=the basal knot enlarged ; 
£t=Suspensor; W1 Wy=roots. (After Bruchmann.) 
of the hypocotyl arise when and where they are required, and are not 
to be held to be clearly defined or constant morphological members.!_ In 
both of the points named it would seem probable that S. spznulosa 
represents a more primitive type than S. AZartensiz. 
Comparing this embryogeny with that of Lycopodium, it seems remark- 
able that the similarity of detail should be so great when the difference 
1 Quart. Journ. Micr. Sc7., xxii., p. 292, etc. 
