BOT.— Vol. I.] CAMPBELL— NAIAS AND ZANNICHELLIA. 55 



although in Zannichellia the flowers are much better devel- 

 oped than in Naias. Whether the quadrilocular anther of 

 the former is to be considered as derived from the unilocular 

 form found in N. jlexilis, through forms like N. major for 

 example, can be better answered after the development of 

 the anther in the latter has been more carefully studied. 



Corresponding to the more highly developed flowers in 

 Zannichellia, the tissues of the stem, especially the vascular 

 bundles, are much better developed. Whether the same 

 difference exists in the roots of the mature plants as is found 

 in the embryos cannot now be stated. A further study of 

 this point would be interesting. 



The embryos of the two agree closely in their earliest 

 divisions, and in both the suspensor remains permanently 

 undivided. It is extremely probable that a further study of 

 embryos of the same type will show that this is a common 

 if not universal phenomenon. In regard to the origin of the 

 different members of the embryo, however, there is one 

 important difference; viz., the origin of the stem-apex from 

 the terminal segment in Zannichellia. In this respect the 

 latter approaches several Commelynaceae and Dioscoreaceas 

 described by Solms-Laubach (1878), where there is a simi- 

 lar terminal origin for the stem-apex. This type of embryo 

 is probably more common than has been supposed, as 

 Hegelmaier's figures of Sparganium (1. c.) indicate a similar 

 state of affairs there. 



Corresponding to the greater part of the embryo devoted 

 to its formation, the root in Zannichellia is better developed 

 than in Naias, and the absence of a root-cap in the latter is 

 also noteworthy, as this is a very uncommon phenomenon. 



Comparing the embryos with those of other Monocoty- 

 ledons, it is seen that in regard to the formation of the 

 cotyledon and stem-apex, Naias approaches the type of 

 Alisma and the Liliaceas, while Zanichellia is more like 

 the type of the Commelynaceae or Dioscoreacese, where the 

 stem-apex is terminal. 



Attention has been called by the writer (Campbell, 1891, 

 p. 253; 1895, p. 518) to the resemblance between the 



(5) Junes, 1897. 



