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 Lvcopodiinn 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 





Embryo* of Seltigiiiclla sf>initUis<i. 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 b, b in Fig. 182 ; / = wall marking off the vascular strand of the axis. 

 A'! A".i = cotyledons ; = ligule; PK=root. E = section of germinated spore with embry 

 in sitn. G, // = seedlings. //, natural si/e ; C, enlarged. 7 r =the basal knot eiilarm-il ; 

 Et suspensor ; W\ Wo = roots. (After Kruchmann.) 



of the hypocotyl arise when and where they are required, and are not 

 to be held to be clearly defined or constant morphological members. 1 In 

 both of the points named it would seem probable that .V. spinulosa 

 represents a more primitive type than S. Martensii. 



Comparing this embryogeny with that of Lycopmihim, it seems remark- 

 able that the similarity of detail should be so great when the difference 



1 Quart, /oiirn. Alia: Si/., xxii., p. 292, etc. 



