CLOSTERHM. 



CLOSTERIUM. 



the internal membrane. A number of trans- 

 parent vesicles are frequently visible in the 

 endochrome, sometimes scattered irregularly, 

 at others arranged in longitudinal series 

 (PI. 10. fig. 43). 



The eudochrome consists of protoplasmic 

 substance coloured green (chlorophyll), and 

 at certain stages, starch is produced in this 

 as in the rest of the Algae. (See CHLORO- 

 PHYLL.) 



The Closteria are reproduced in various 

 ways. The individuals divide, like the rest of 

 the Desmidiaeese, the separation taking place 

 transversely in the situation of the transpa- 

 rent space, where two new half-cells become 

 developed, subsequently separating. As 

 these new ' halves ' are often very small at 

 the epoch of separation, specimens occur 

 with the two portions very unequal. An- 

 other mode of reproduction is by conju- 

 gation. In this, a pair of individuals become 

 united somewhat in the same way as in the 

 Zygnemacese. Ordinarily, the individuals 

 conjugate by the convex side. The process 

 is described as follows: The outer mem- 

 branes of the parents split circularly in the 

 situation of the central transverse space ; a 

 delicate internal membrane is protruded from 

 each, as a sac, and these meet and coalesce. 

 Sometimes the sacs are in pairs from each 

 parent-cell. (See CONJUGATION.) When 

 the cross process is complete, the contents 

 of both parent- cells pass into it and become 

 collected into a globular or squarish cell 

 (PI. 10. fig. 42 & 46). Different statements 

 are made with regard to the ultimate history 

 of this, and it is probably variable. Morren 

 states that it becomes a moving gonidium ; 

 while most authors state that it becomes a 

 resting spore with firm membranous coats. 

 Again, Morren describes the segmentation of 

 the green contents of this spore or gonidium 

 into a number of portions, each of which 

 becomes a perfect individual. Focke gives a 

 figure which seems to bear out this state- 

 ment, and it would find an analogy in the 

 mode of reproduction by active gonidia in 

 Pediastrum, described by Caspary and Al. 

 Braun. (See PEDIASTRUM.) Focke also 

 figures a condition of Closterium Lunula in 

 which the whole of the green contents of an 

 individual cell had become retracted from the 

 walls, and converted into a number of green 

 globular bodies, with proper coats, resem- 

 bling the resting spores found in many fila- 

 mentous Algae under certain conditions. 

 (See (EDOGONIUM and SPIROGYRA.) 

 The Closteria are capable of fixing them- 



selves by one extremity to foreign bodies, 

 and Ehrenberg asserted the existence of a 

 footlike organ; but no such structure seems 

 to exist. The individuals also possess a 

 power of moving in water, but the nature of 

 this is inexplicable at present. The seg- 

 ments of the outer membrane separate from 

 each other when their contents decay, and 

 when they are dried. The membrane is co- 

 loured blue by sulphuric acid and iodine 

 (cellulose); in its natural condition it often 

 has a reddish tint, especially towards the 

 ends. 



Analysis of species (British) : 



fCell suddenly narrowed at the ends r attenuatum, 



l.<| into a conical point \ 1.1-57". 



I Cell not suddenly narrowed 2 



Cell striated, tapering into a beak at 

 ends, lower margin prominent at 

 middle 3 



2. Cell very minute, beaked, straight,not f Griffithii*, 



striated, nor lower margin promi- < 1. i-300 to 



nent at middle I 1-450". 



Cell not beaked; if striated, lower 



margin not prominent at middle .. 6 

 f Beaks setaceous, as long as or longer 



3. than body 4 



I Beaks linear, much shorter than body 5 



f Beaks much longer than body { ^L^I Jgt/ 



4> \Beaks about as long as body {'if^JR 



f Cells much inflated at middle, rapidly r Ralfsii, 



I tapering at ends I 1. 1-79". 



5 '| Cell slightly inflated at middle, gra- f lineatum, 



I dually tapering at ends 1 1. 1-48". 



fCell minute, acicular; sporangium 



fi ) cruciform 7 



' 1 Cell not acicular ; sporangium orbi- 



L cular 8 



'Ends obtuse {"hTuO". 



("Cell semilunate or semilanceolate, 

 lower margin inclined upwards at 



_ ) ends 9 



**1 Cell with either truncate ends, or 

 lower margin inclined downwards 

 I at ends 12 



g J Vesicles numerous, scattered { j i^GO" 



L Vesicles in a longitudinal row 10 



f Ends of cell slightly curved upwards ; f turgidum, 



10. J longitudinal striae distinct \ 1. 1-39". 



| Ends of cell straight , striae none or 



I indistinct 11 



f Cell linear-lanceolate ; ends conical, ( acerosum , 



llJ obtuse il.l-70tol-58" 



*-Cell semilanceolate; ends subacute -j a ? C fg"// W7n ' 



f Cell not striated, crescent- shaped . . 13 



12. < Cell either not orescent- shaped, or 



I. else distinctly striated 17 



r Vesicles numerous, scattered { j ''i!^'^"' 



13. i Vesicles in longitudinal row 14 



v Empty cell colourless, ends rounded 15 



14. Empty cell usually reddish, ends 



subacute 16 



* PI. 10. figs. 57 & 58. 



t PI. 10. figs. 45 & 46 (Conjugation). 



J PI. 10. fig. 40. 



$ PI. 10. figs. 41 & 42 (Conjugation). 



