A Theory of the Double Leaf-Trace. 81 
have been found between this case and the presence of small 
laterals such as is customary in the type of seedling first described, 
in which they fuse with the central bundles high up in the 
cotyledon and have no influence upon the symmetry of the root. 1 
TETRARCH TYPE. 
Fig. 2. Series showing transition features from cotyledons (a) through 
hypocotyl, ( b ) to root ( c ). Protoxylem black; metaxylem cross-hatched; 
phloem white. 
A striking intermediate form is found in Liriodendron 
tulipifera, Clematis Hendersoni and in some Composites. Here 
the persistent, though slender, laterals penetrate into the hypocotyl, 
fuse with the corresponding bundles from the opposite cotyledon, 
and even begin to assume root characters but ultimately die out, so 
that the root is diarch (text-fig. 3). 
INTERMEDIATE TYPE. 
Fig. 3. Transition features in Liriodendron , etc. 
II.— Structure of Gymnosperm Seedlings. 
The publication of Matte’s 2 paper in 1904, together with its 
interesting, but somewhat scanty description of the transition 
1 see footnote 6. p. 80. 
2 H. Matte. “ Recherches sur l’appareil libero-ligneux des 
Cycadacees.” Caen, 1904. 
