Seedling Anatomy of Certam Sympetalae. II. 
305 
Types of Venation in the Cotyledons. 
The venation of the cotyledons in the Compositae is perhaps one of 
the most remarkable features in the seedlings examined. In Diagram I, in 
which the vascular bundles are represented by dotted lines and crosses, the 
five types of venation observed are given. It must be remarked that in all 
cases the smallest bundles have been omitted from the diagram. 
Type V, which was seen in only one example — Cichorium Intybus — is 
one of the simplest. Although several bundles are present in the upper 
portion of each seed-leaf, only a single one enters the hypocotyl, and, as 
will be seen later, this is associated with the simplest type of transition. 
1 II III IV 
Diagram i. Types of venation in the cotyledons, a — apex, b = base, and c =» transverse 
section of base of cotyledon. Vascular bundles represented thus - - - - and x. 
Type I, also, is very simple, but here three bundles enter the hypocotyl. 
The remaining ones are really variants on I and V. In II and ill the chief 
strands are more numerous, but they arise in the same manner as in I and V. 
At the base of the cotyledon in II (as in I also) there are three vascular 
strands, but in III five well-marked bundles enter the hypocotyl. Type IV, 
which is seen in Arctium majus , differs from I chiefly because of the peculiar 
branching of the chief strands near the apex of the cotyledon. This will be 
described later under the species. 
Two rather remarkable facts in connexion with the venation must be 
noted. The first is that, so far as has been observed, the chief strands never 
end blindly in the tissue of the mesophyll. The branches which arise near 
the base of the seed-leaf, whether from the midrib or from the laterals, 
generally pursue an arcuate or sinuous course and reunite with the bigger 
