Hill and de Frame . — On the 
198 
S. cerastoides conforms to type, whilst N. Vaccaria and S. vulgaris fall into 
the next category. Of the Aizoaceae, Mesembryanthemum , the cotyledons 
of the species of which show no differentiated petioles, is to be included in 
the present class, whilst Tetragonia is to be placed in the next. 
B. Those in which the lateral strands, generally one on either side of 
the main bundle, extend down as far, or nearly as far as the insertion of the 
seed-leaves, or in some cases even into the hypocotyl, before fusion with the 
central strand takes place. Examples : The Amarantaceae, with the ex- 
ception of Amaranthus sy Ives tris and species of Gomphrena , which approach 
Class A ; the Chenopodiaceae, with the exception of Chenopodium ambro- 
soides, C. Botrys , A triplex thamnoides , Kochia , Corispermum , and Suaeda 
dendroides , which belong rather to the previous class; and, lastly, the 
Phytolaccaceae. 
5. A comparative examination of these facts shows that differences 
sometimes occur in different examples of one species ; the dissimilarities 
between some species of a genus may be greater than the differences between 
genera; further, Pup alia, Clay to7iia, and Salicornia , genera widely separated, 
show very close resemblances. 
6. With regard to the Nyctaginaceae, the transition phenomena may 
be looked upon as a modification of type 3, for after each cotyledonary 
strand has bifurcated and isolated within the blade of the seed-leaf those 
protoxylems situated in the cotyledonary plane, corresponding bundles 
from opposite sides together form the two protoxylem poles situated in the 
intercotyledonary plane. To this, however, Abronia is an exception, three 
poles of the root-structure being formed from the bundles of the larger 
cotyledon, and the remaining pole from the vascular tissue derived from 
the smaller seed-leaf. 
7. A connexion between the Nyctaginaceae and the other Natural 
Orders of the Cohort may be traced. For example, in Amaranthus sylvestris , 
Gomphrena globosa , G. Haageana , Phytolacca paraguayensis , and P. dioica, , 
the protoxylem is isolated in the cotyledons ; in Amaranthus, Gomphrena, 
and other plants there is, in the axis, a delay in the fusion of the four 
phloems ; in other words, for a certain distance downwards the structure is 
incompletely tetrarch. In this connexion it will be remembered that it is 
not at all uncommon for the initial tetrarch structure in the Nyctaginaceae 
to be reduced to diarch. 
8. Without entering into any theoretical considerations — they will be 
published later — it may be pointed out that the Nyctaginaceae have by far 
the largest seedlings as compared with the other Natural Orders of the 
Cohort ; that the vascular bundles of the large cotyledon of Abronia form 
three of the four poles of the root-structure, the remaining one being from 
the traces of the small seed-leaf ; and that in the much smaller seedlings of 
the orders other than the Nyctaginaceae a difference is often found in the 
