SPIROGYRA. 



[ 598 ] 



SPIROGYRA. 



texture and separated by an interval from 

 the next, which is brownish and of firm tex- 

 ture. The inmost coat, or true spore-mem- 

 brane, is again delicate. The spores appear 

 to rest through the winter after they are 

 formed and to germinate in spring, in which 

 process the middle coat of the spore splits at 

 one end, longitudinally, opening by two 

 valves to allow the inner to grow forth, 

 which bursts through the outermost sac, in 

 the form of a tube (PI. 5. fig. 19) which 

 soon acquires the characteristic appearance 

 of the parent plants. The contents of the 

 spore are brown and homogeneous during 

 the stage of rest (fig. 21); in germination 

 they become green again, and arrange them- 

 selves in the spiral bands (fig. 22), which 

 become more distinct as the cell elongates. 



Certain other occurrences take place in 

 the cell-contents of the Spirogyrce, the rela- 

 tion of which to the reproduction is not so 

 clear as the above. In filaments in an un- 

 healthy condition, about to die, such as are 

 often seen when a collection of them is placed 

 in a jar of water to keep for examination, it 

 is not uncommon to see the green contents 

 gradually lose their spiral arrangement, and 

 break up into a number of globular portions 

 (PI. 5. fig. 28). We have sometimes ob- 

 served these rolling over slowly in the cell. 

 In one case we have observed the contents 

 converted into sixteen distinctly organized 

 biciliated zoospores (PI. 5. fig. 20), differing 

 only from the ordinary zoospores of the 

 Gonfervoids in the almost total absence of 

 colour. They were somewhat crowded in 

 the cell, and moved lazily about in it, the 

 cilia vibrating. It is still more common to 

 observe the contents of decayed filaments 

 converted into encysted globules (PI. 5. figs. 

 24, 25), which would appear to be a kind of 

 resting-form of the zoospores. These glo- 

 bules, which have a tough spinulose coat, 

 have been observed by Pringsheim as pro- 

 duced from the contents both of ordinary 

 cells and (abnormally ?) from the contents of 

 a large spore (PI. 5. fig. 23) : the latter case 

 might give colour to the idea that this was 

 a sporange, had not its germination been 

 observed. Pringsheim has further noticed 

 that actively moving zoospores are produced 

 from the small encysted bodies; perhaps 

 these may fulfil an antheridial function. We 

 are compelled to treat thjs subject some- 

 what briefly, but must direct attention to the 

 relations of the CONJUGATION to that of 

 the DESMIDIACE^, and those of the large 

 spores and smaller globules to the similar 



bodies in the Desmidiaceae and in the Vol- 

 vocineae, as well as in the other Confer- 

 voids. 



The species of Spirogyra have been greatly 

 multiplied by authors. The peculiar fold 

 projecting from the septum appears to us to 

 depend upon age and activity of growth ; 

 and the length of the joints depends greatly 

 on the stage of growth, as they continually 

 divide into two equal parts. 



Spiral band single. 



1. S. tenuissima. Vegetating filaments 

 1-3000" in diam.; joints four or five times 

 as long; spiral band open; spore oblong - 

 elliptical (Hassall, pi. 32. figs. 9, 10). 



2. S. longata. Filaments about 1-1000'' 

 in diam. ; joints six or eight times as long ; 

 spiral lax; spores oblong-elliptical (Hass. 

 pi. 31. fig. 394, pi. 28. figs. 3, 4?). 



3. S. inflata (S. gastroides, Kiitz.). Fila- 

 ments 1-1680" in diam.; joints four or five 

 times as long ; turns of spiral about five ; 

 fertile cells ventricose ; spores oblong-ellip- 

 tical (Hass. pi. 32. figs. 6, 7). 



4. S.communis(fig.673). Filaments 1-1 440 

 to 1-1200" in diam.; joints two or three 

 times as long ; turns of spiral four, broad ; 

 spores elliptical (Hass. pi. 28. figs. 5, 6). 



5. S. quinina (PI. 5. fig. 17). Fila- 

 ments 1-600" in diam.; joints one and a 

 half or two times as long; turns of spiral 

 broad and dense; spores elliptical (Hass. 

 pi. 28. fig. 2). Varies to some extent in the 

 length of the joints, which are sometimes 

 two to seven times as long. 



Spiral bands two. 



6. S. decimina. Filaments 1-720" in 

 diam. ; joints two or four times as long ; 

 spiral bands lax, crossing so as to present 

 the appearance of a row of the letter X 

 (Hass. pi. 23. figs. 3, 4). 



7. S. elongata. Filaments 1-1320 to 

 1-1200" in diam. ; joints ten times as long; 

 spiral bands lax (Berkeley, Gleanings, p. 12. 

 fig. 2). 



Spiral bands numerous. 



8. -S. nitida (PL 5. fig. 26). Filaments 

 1-360" in diam.; joints twice or three times 

 as long ; spiral bands four, dense, closely 

 veiled ; spores elliptical (Hass. pi. 22. figs. 

 1,2). 



9. S. maxima. Filaments 1-200 to 1-300" 

 in diam. ; joints equal, one and a half times 

 or twice as long; spiral bands lax; spores 

 globular (Hass. pi. 18, 19). 



