90 Dr. F. Cohn on the Development and Propagation 



face of the spores ; their body is converted into a drop of muci- 

 lage and loses its form ; it appears as if a portion of the substance 

 was absorbed endosmotically by the spore : a formal penetration 

 of the spermatozoid into the spore certainly did not take place, 

 for a remnant of it, perhaps the reddish drops, can long be 

 seen attached upon the outside of the spore. However, Sphce- 

 roplea is not very well adapted for the investigation of the real 

 act of impregnation, on account of the want of transparency in 

 the green spores, notwithstanding that it offered an exceedingly 

 favourable object for the earlier processes. 



After a short time the impregnated spore becomes enveloped 

 by a true cell-membrane, which at first can only be detected by 

 the contraction of the contents by reagents, but subsequently 

 can be readily seen by direct inspection, as it gradually separates 

 further from the cell-contents. A second membrane is soon 

 produced beneath the first, the second being originally in close 

 contact wdth the contents of the spore, but subsequently folded 

 in the stellate manner above described ; the uppermost, earlier- 

 formed coat is next thrown off, and such coats are found in the 

 sporangial cells as empty vesicles among the spores — a ' moulting^ 

 or ecdysis already observed by Al. Braun. Finally there is pro- 

 duced under the stellate coat a smooth membrane, so that the 

 impregnated spore of Sphceroj)lea bears an analogy with those of 

 Spirogyra and Zygnema, and possesses likewise the three coats, 

 the outermost of which however is thrown off, not in germi- 

 nation, but even before the spore is ripe. The contents of the 

 spore are originally of a uniform green colour, in which several 

 Starch-granules make their appearance ; subsequently they be- 

 come opake, and pass through olive-green and reddish-brown, 

 finally into a pure red. The number of the spores depends 

 upon the quantity of chlorophyll which was present in the spo- 

 rangial cell ; their size is also very variable according as more or 

 less of the green plasma is applied to the formation of one 

 spore ; although they are usually from y| j to y^^j of a line iii 

 diameter, spores also occur which have double and even 100 

 times that magnitude ; I observed elliptical spores which attained 

 ^i_j _i_^ even ^^j of a line in the long diameter; I once met 

 with a monster spore y^ ^^ ^ ^^^^^ ^^ *^^ \on^ diameter, the red 

 contents being enclosed in the papillose spore-coat just as usual. 

 The approximate or distant arrangement of the sjwres, in one 

 or several rows, is also liable to variation. 



Sphcerojdea annulina, although it always occurs as a multi- 

 cellular filament, must be regarded as essentially a unicellular 

 plant, in Nageli's sense, since all the cells, without exception, 

 even the terminal capillary-pointed cells included, take part in 

 the propagation, and therefore the whole filament can only be 



