414 Prof. H. Karsten on the Formation, 



cavities or vacuoles are formed, whicli separate the rest of the 

 granular mucilaginous contents into two portions, — namely, a 

 central portion surrounding the nucleus, and a peripheral one, 

 lining the inner surface of the primordial sac ; but the two are 

 united by simple or branching fibres extending between them. 



In the cells of Cladophora no nucleus is visible. Their plasma 

 is described as mucilaginous, of greater density at the surface 

 contiguous to the second inner cell, where it contains much 

 chlorophyll and starch (and, according to Nageli, hardens to 

 form the inner sac [InnenschlaucK]). The state of matters in 

 this instance, however, is somewhat different ; and a thorough 

 discussion is necessary to enable us rightly to estimate the 

 organization of these cellular plants, as also that of the plant-cell 

 generally. 



The contents of Cladophora glomerata, which escape when a 

 section of the plant is made under water, are for the most part 

 readily destroyed by the action of the water, so that only the 

 corpuscles of chlorophyll and starch, and, at a later period, only 

 those of the latter, can be discerned. These starch-vesicles 

 frequently constitute the nuclei of the chlorophyll-grains, and 

 advance in growth within them during the liquefaction of their 

 substance. Further observation of the exuded substance of the 

 wounded joint of the Conferva, whilst submitted to the action of 

 water, will show that this apparently mucilaginous fluid consists 

 of hyaline vesicles and cells, which are filled with a transparent 

 liquid, either quite colourless or in part coloured by a greenish 

 matter. The latter, where present, adheres like a green mucilage 

 to the surfaces of the very delicate envelope of the cells, coats them 

 externally or internally, and often entirely fills their cavity. The 

 size of these vesicles varies from the most minute to others whose 

 diameter considerably exceeds the transverse diameter of the 

 Conferva. However, the determination of their original dimen- 

 sions is very difficult ; for all of them, at the moment the section 

 of the Conferva is made, and upon coming into contact with the 

 water, undergo an extraordinarily rapid and considerable disten- 

 tion, and mostly soon rupture. By causing movements in the 

 water, the escaped delicate and yet unruptured cells may be 

 made to roll and demonstrate the resistance to water which their 

 membrane enables them for some time to maintain. Moreover 

 similar delicate cells may be observed in the emptying portion 

 of the cut joint-cell, adhering here and there to the inner surface 

 of the secondary membrane. The central cavity of the joint-cell 

 becomes eventually filled with water, or, it may be, with air, if 

 the latter has been allowed to enter during the making of the 

 section. 



Several small vesicles and thin-walled cells, of the same sort. 



