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178 BOTANICAL GAZETTE [September 



(2) "The flowers of Naias represent the simplest form which an 

 angiospermous flower can assume, consisting simply of a single carpel 

 with but one ovule, or of a single stamen which in most species has 

 but one pollen cavity" (Campbell 3, p. 12).. The inaccuracy of the 

 last statement can be easily shown. By sorting out the species 

 described in Rendle's paper, it is found that seven species have a 

 unilocular anther, while twenty-three have the usual quadrilocular 

 anther. ISIoreover, Campbell figures a case where the anther of iV. 

 flexilis is partially divided by a partition. It would seem then that N. 

 flexilis forms an exception to the condition obtaining in the genus, 

 hence the similarity between megasporangiate and microsporangiate 

 structures is not so great as supposed. Concerning the single stamen, 

 it by no means follows that this necessarily indicates a primitive con- 

 dition, for there are cases of monandrous flowers belonging to families 

 which are admitted to be high in the scale, for instance Hippuris and 

 many orchids. 



(3) The ovary of N. marina is surmounted by three stigmas 



(sometimes two), that of N, microdon by three stigmas, or by two 

 stigmas and a spine-arm, or by intermediate conditions; other species 

 show a varying number of stigmas (see Rendle's figures). The 

 number of stigmas in a flower is usually taken to indicate the number 

 of carpels, e. g., some grasses have two stigmas though there is only 

 one seed. In the case of Naias, Eichler (10) is of the opinion that 

 the evidence is untrustworthy, since the stigmatic branches are of 

 relatively late appearance. It may be, how^ever, that we have here a 

 relic of the condition of the flower with several carpels. 



has unisexual flowers, monoecious or dioecious; this is 

 not regarded as being so primitive a condition as the hermaphrodite 

 one exhibited by members of the Potamogetonaceae. 



(5) PoUination in Naias is effected by means of the water in which 

 the plants are immersed. This mode must be considered to be derived 

 from the anemophilous mode, for non-motile spores in the higher 

 plants are regularly carried through the air. 



Naias 



me 



for Naias cannot be maintained. The evidence goes to show that its 

 structure is reduced in accordance with its aquatic habit. The genus 

 stands very much isolated, but it has been suggested bv Magnus that 



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