ON NAIAS GBAMTNEA DEL., VAE. DELILEI MAGNUS. 



21 



The fruit is sculptured with a network of raised ridges 

 which thus produce depressions in the shell; this sculpture 

 seems to have its seat in one of the inner membranes of the 

 shell, since it oannot always be distinguished through the most 

 external layer. As far as I have been able to make it out, 

 it is somewhat after the character of the accompanying fig. 84; 

 but this must be looked upon as a diagramatic interpretation 

 of what is supposed to be seen, rather than an actual repre- 



Fig. 84. 



sentation of fact. In the same way I have drawn the testa of 

 Naias flexilis in fig. 85 from a single mature fruit in one of Dr. 

 Boswell's Loch Cluny specimens ; I am more sure of the cor- 

 rectness of this figure than of that of JV. graminea, but it 

 represents what is seen in a single fruit only. It would there- 

 fore appear that the sculpture of JV. flexilis is quadrangular, 

 while that of JV. graminea is hexagonal ; but too much must 

 not be made of observations founded on such a limited basis. 



According to the observations of Cesati* the fruits of the 

 Italian JV. alaganensis are granulose-punctate, which fairly well 

 describes the appearance of the outer covering of the Manchester 

 plant; but Cesati's figure in 'Linnsea,' I.e., Table ii., fig. 2d, 

 makes the fruit much more papillate than I find it in the Lancashire 

 form. On the other hand, this same observer makes the fruit of 

 JV. flexilis shining and obscurely angular, and he so draws it in his 

 plate. 



The explanation of this difference in the form of sculpturing is 

 probably due to the fact that the external membrane more or less 

 obscures the underlying layer, and thus the latter is seen by 

 observers according as the transparency of the outer layer admits 

 of it. For the further elucidation of this point I have reproduced 

 the figures of Dr. Magnus in Plate 252, where figs. 40 and 41 show 

 the arrangment of the coats of the fruit of JV. graminea from Cairo, 

 and figs. 37 to 39 those of JV. flexilis. 



At Reddish mature fruits of JV. graminea are produced in great 

 abundance ; scarcely a plant occurred without fruits. In the many 

 hundred plants which I have examined I have not seen a single 

 instance where the beak of the fruit was other than bifid, unless 

 it had broken off altogether, as represented in figs. 81 and 83, 



* " Die Pflanzwelt im Gebiete zwischen dem Tessin, dem Po, der Sesia und 

 den Alpen," (' Linnffla,' vol. xxxii., 1863, pages 259 and 260). 



