14 ON NAIAS GEAMINEA DEL., VAB. DELILEI MAGNUS. 



on the same Plate at the points marked 6. In the upper part of 

 fig. 32 the single cell seems to have been multiplied into three, but, 

 as Dr. Magnus explains in his memoir, these long Y-shaped cells are 

 arranged in a single linear series at the edge of the leaf; the 

 bifurcating end of one cell encloses the solitary attenuated end of 

 the one next to it ; a section at such a junction severs the three 

 interlocked ends of two contiguous cells. 



The absence of this libriform tissue in the Lancashire plant has 

 a bearing in determining its source of origin, as will be noticed 

 further on. 



Between the Italian and the Lancashire plants I notice one 

 other point of difference, which may be due to the period of growth. 

 Above and below the central bundle of the leaf, but particularly on 

 the lower surface, the external cells are densely packed with starch- 

 grains, very similar to what is met with in the external membrane 

 of the fruit. Although starch-granules are present in the membrane 

 of the fruits of the Lancashire plant, I have failed to discover a 

 single instance of their occurring in quantity in the leaves. 



All the cells of the leaf exhibit a very striking circulation of 

 their contents against the cell-walls ; the chlorophyllean granules 

 and other protoplasmic bodies being very large, and the cell-walls 

 being very transparent, the plant furnishes a splendid illustration 

 of circulation, more so than in any plant which I have examined. 



IX. — The Inflorescence. 



The construction of the flowers of the genus Naias and their 

 morphology have been minutely studied by Dr. Magnus, and the 

 results given in his 'Beitrage,' pp. 26 to 33. In referring to the 

 development of a side-shoot of N. graminea he says that many of 

 the internodes are suppressed, and that from three to five pairs of 

 leaves spring from the axis before we reach the flowers, which occur 

 to the number of from two to four all in one node. He adds that 

 it is worthy of notice that the male flowers are found on those parts 

 of the shoots which have long internodes, while the female flowers 

 occur only on those shoots where the internodes are suppressed. 



This was not the structure in the Lancashire 

 plant. Quite as often as not pistilliferous flowers 

 were found in the axil of the first pair of leaves of 

 the tuft. Antheriferous and pistilliferous flowers 

 are found side by side (see figs. 67 and 68) in the 

 axil of the same leaf. Both kinds of flowers are 

 also found in all stages of development, quite young 

 ones lying side-by-side with those more developed. 

 The great majority of the plants produced fully- 

 Fig. 67. developed flowers, both male and female, the latter 



being much the more numerous. The species is 

 monoecious ; even in those instances in which I found only female 

 flowers on the individual plant, I could not be sure that male 

 flowers had not been produced, or would not have been produced later 

 on. It was not usual, though by no means infrequent, to find both 



