Seedling Structure of certain Centrospermae . 197 
2. In all the first-named orders the differences which obtain between 
the various species are chiefly connected with the levels at which the transi- 
tion phenomena first appear and end, and the level at which the lateral 
strands of the seed-leaves effect a junction with the divided central cotyle- 
donary bundle. 
3. With regard to the first point, the plants may be divided roughly 
into three classes : 
A. The bundle from each cotyledon enters the hypocotyl in an undivided 
state, with the protoxylem in the endarch position. Examples : Claytonia 
perfoliata , Pupalia purpurea , Salicornia europaea , S. perennis , and S. 
Smithiana . 
B. The main seed-leaf-bundle bifurcates at a level just above the 
cotyledonary node. Examples : Dianthus barbatus , D. arenarius , Lychnis 
Viscaria, Gypsophila Saxifraga , Saponaria cerastoides , Vaccaria , 5 . vul- 
garis, Tunica prolifer a, Cerastium perfoliatum , Stellaria gr amine a, Mesem - 
bryanthemum spp., Cucubalus baccifera , and Spergularia salina . Of these 
the first one is intermediate between Classes A and B, whilst the last two 
are intermediate between Classes B and C. 
C. The main seed-leaf-bundle bifurcates at a much higher level, some- 
times even in the base of the blade of the cotyledon. 
All the other species examined, and these comprise the majority, fall 
into this class ; of them, the following show the isolation of the protoxylem- 
elements either in the petioles, e. g. A triplex hastata , or in the lower regions 
of the blade of the cotyledon, e. g. Amaranthus sylvestris , Gomphrena 
Haageana, G. glob os a, Phytolacca paraguayensis , and P. dioica. 
This feature is not constant in the genera; thus A. sylvestris was the 
only species of the genus Amaranthus which exhibited it ; also it was not 
observed in Phytolacca acinosa. 
Another character shown by some of the members of this class is the 
delay in the fusion of the phloem-masses of the otherwise normal diarch 
root-structure. Examples: All species of Amaranthus and Beta, A triplex 
hastata , A. thamnoides , Obione portulacoides , Kochia trichophylla , and Cori- 
spermum hyssopi folium. 
4. With regard to the second point, relating to the lateral bundles, it 
may be remarked that in very few cases are these strands corresponding in 
importance to the laterals, say, of Dahlia Merckii ; also it is rather difficult 
to make a satisfactory classification, for much depends on whether the seed- 
leaves have well-marked petioles or not. Roughly, the plants examined 
fall into two categories : 
A. Those in which the lateral bundles of the blade do not extend 
down to the cotyledonary node but fuse on to the main seed-leaf-strand at 
the top of the petiole or a relatively high level. This is constant in the 
Portulacaceae, and in the Caryophyllaceae with the exception of Saponaria . 
