.).»} CONTRIBUTIONS PROM Nil NATIONAL HERBARIUM. 



nature into small groups as to render easy their availability 



in at ill-- present time that other purpi - • i i law fi< ation, 



the indication of relationships * Ay But unless ;ill the usual 



i the distinct ions dra* d by \\ illiam 

 Smith must l» i .1- too unimportant and especially too unstable to admit of 



adoption. 



• most painstaking and thorough analysis o! Navicula is that of Cleve in 

 I - Saviculoid Diatoms ■ I regret 1 cannot follow his divisions of this genu I 

 would I" aside fmm the p 1 i" discuss in ample detail the ra< 



It must, therefore, Buffice to say that a careful reading of the 

 chapter "On the value of the charai I of that work, will, in connec- 



tion with the divisions of Navicula subsequently made in the work, reveal th< 

 that nearly .ill the characteristics there looked upon as inadequate are subsequently 

 employed as liases for the n-\\ genera created. I therefore follow in general the 

 iy of authors writing since Cleve's work appeared, in considering these distinc- 

 tions of value for Bubgeneric grouping, though nol of generic worth. Esp< cially has 

 Van Beurck* grouped the genus Navicula in a way satisfactory to the writer Excep- 

 tion must, however, be taken to his recognition of the genus Stauroneis Ehrenb. 

 \- Van Beurck there says the true Stauroneis forms differ in 

 spect from Navicula, except "by the central nodule being transversely dilated 

 into ;i st luros " This has always appeared to me to be a very trivial ground The 

 stauros is a most common accident of many Bpecies in Bevi ral other g< nera, as Ach- 

 nanthes Bory, in .1. coarctata (Breb.) Grun.;^ Pleurosigma W. Smith, in /'. asiaticiim 

 Temp. & Brun and P. staurophorum Grun.;d and ' occoneis Ehrenb., in I 

 Brun.< Nor i> this any more or less tin- "dilation of the central nodule-' in the one 

 case 1I1. m in the other. In short, the separation of stauros-bearing forms into ;1 genus 

 is an impossibility, either inside the genus Navicula or outside of it . 



I look upon the following genera as having fairly g 1 claim to separate standing 



Jo, j Thwaites, for reasons si ited under that genus; Dictyoneis Cleve, on 

 account of its peculiar.internal platesand especially its loculate border, / though it 

 possibly be necessary to unite it with Mastogloia; Rouxia Brun A Berib.;?also 

 the following six genera, which, although separate from Navicula, Bhould 1>»- united 

 under the same generic name: Frustulia C. Ag., in pan . Berkeleya Gre\ Van Heur., 

 Reicheltia Van Beur., Amphipleura Kin/... Brebissonia Grun., Vanheurckia Breb., 

 for all which see under Frustulia in this report; also their figures and descriptions 

 by Van Beurck. h 



To ih<' foregoing maybe added Cleve's genus Cistula;' for although ii at present 

 includes only the single species C. lorenziana (Grun. Cleve, this i- perfectly constant 

 and strikingly unlike other naviculoid diatoms. < >n the whole the best conception of 



cula and its allies i- that of Van Beurck. j 

 Navicula aestiva Donk. Trans. Micr. Soc. Lond. n. s. 6:32. pi. S. 1. 18. 1858; Brit. 

 Diat.6. pi. l.f. 8. 1871 73. Schmidt, Atlas pi. l.f. 8,10 11 (unnamed), pl.S 

 type /'. si unnamed). 1875. Rabh. I'l. Eur. Alg. 1: 184. 1864. DeToni, Syll. 



" Sv. Vet. Akad. Bandl. 26 : 1894; 27 : 18 

 b Van Beur. Treat. Diat. 18 



n Beur. Synop. />/. :>>.(. 18 1881. 

 1' i.e.- Le Diatomiste 1' 5 : pl.8 1 I ■ 1891. 



- hmidt, Ail. 1- pi. m.f. \e 1894 



Sv. Vet. Akad. Bandl. 26': 124. L894; and Van Hour Treat. Diat. 157. 1896 

 9 Berib. Diat. Auverg L56 I - 



Ho,,, Treat. Diat. 239, 242 245. I- 16 



- Vet \ka-l. II mdl. 26': 124. L894 



Beur. Treat. Diat. 162 237. 1896. 



