1 68 Blackburn . — ■ On the Vascular Anatomy of 
none of the peculiarities of anatomy exhibited by the other species, and 
conforms to the general type described for the family. 
The vascular cylinder consists of a ring of collateral bundles (see 
Text-fig. it). 
Each foliage leaf supplies three leaf-trace bundles and the insertion is 
trilacunar. The plumular strands reduce to six above the cotyledonary 
node. The cotyledons also usually have three strands at their base, though 
one or both of the laterals may be missing (see Text-fig. n, inset). 
At the cotyledonary node the central strands behave as usual, and the 
laterals insert themselves in the gaps of the plumular tissue (cf. Clematis 
viticella :). The lateral strands fail to form intercotyledonary poles, and 
a diarch root is obtained. 
Secondary thickening begins at an early age, and differs from that 
Text-fig. 12. Ranunculus arvensis. First plumular node, primary structure disguised by 
secondary thickening. Inset shows relation of part shown ( x ) to other parts of the section. 
described above for other genera of the order in the absence of principal 
medullary rays and consequent production of a continuous vascular cylinder. 
The condition thus produced is suggestive, in appearance, of a siphonostelic 
ring, but is clearly secondary in origin (see Text-fig. 12). An endodermis 
could not be detected in young seedlings, but in older plants indications 
were sometimes seen. 
2 . R. acris may be taken as a type of the second group of forms 
found in this genus. The seedlings of this species show considerable varia- 
tion. One young seedling bearing only a single foliage leaf appears very 
similar to R. arvensis at the same age, but it is very much smaller in size 
and the entering leaf traces have a horizontal course. The usual six 
plumular strands at the cotyledonary node are not distinguishable. In 
another seedling of apparently the same age, the primary vascular bundles 
