Sometimes this condition, that of the amphiphloic 110 plostele, is maintained throughout the adult stem (Lindsaya).
S.Amphiphloic haplostele of -trace and leaf-gap. FIG.
This type of stern is therefore often spoken of as protoslelic. In the Ferns there is clear evidence that the amphiphloic haplostele or protostele succeeded the simple (ectophloic) protostele in evolution, and that this in its turn gave rise to the solenostele, which was again succeeded by the dictyostele.