64 



plumule, showing the first leaf (L^), coming out at the 

 very base of the cotyledons, and borne on a distinct, straight 

 hypocotyl (C), at the base of which is a wreath of long root- 

 hairs ; we see further the primary root, which is relatively 

 short and unbranched. The whole germinating plantlet, 

 except the root and the lowest part of the hypocotyl with 

 the wreath of root-hairs, is now above ground, the testa of the 

 seed is soon dropped and the cotyledons now spread out, 

 being perfectly flat, green and entirely different from the later, 

 the pitcher-shaped leaves. Fig. 25 shows a somewhat later 

 state, where the first leaf has attained its full size and final 

 shape, not differing essentially from the typical leaf of 

 this species. It is an interesting fact that there are no 

 transition-forms between this, the first leaf (Fig. 27), and the 

 later ones. The hypocotyl is straight for some time, and the 

 primary root growls slowdy in length and does not show any 

 ramification until later. The leaves now begin to develop, 

 forming a dense rosette near the surface of the ground ; 

 the cotyledons fade away, and, while the primary root 

 has attained its final length, the secondary roots begin to 

 grow at the upper part of the hypocotyl, just below the cotyl- 

 edons. But before this stage, figured in Fig. 26, the plant 

 has undergone some changes : the plumule, hitho^-to kept a 

 little above the surface of the ground, has now gradually been 

 moved downwards by the bending of the hypocotyl, a conse- 

 quence of the zigzag direction of the primary root, which 

 very soon disappears. By this mechanical movement the 

 wtiole plant attains its final position in the soft mass of 

 Sphagnum and is able to continue its growth and produce 

 leaves and flowers. 



PAPAVERACE^. 



Sangiimaria Canadensis. 



Germinating plantlets of this species were collected at the 

 end of April in shaded places in the woods on the shore of the 

 Potomac, where the plant occurs in great abundance. The 

 . , seed germinates deep under ground, and the cotyledons never 

 appear above the soil. They (Plate VII, Fig. 29) are oblong, 

 obtuse, red and fleshy, and contain deep red juice like the 



I 



> 



-^ 



m 



t 



