300 ON THE GERMINATION OF CHAEA. 



spirally investing tubes lying immediately upon the oospore, and the 

 wall of the basal turning-cell abutting on the oospore, take part in the 

 formation of the shell, and the outer surface presents more or less 

 raised stripes corresponding to the spirally investing tubes. ^ The 

 shell is smooth at the point of union with the oospore, and terminates 

 in a short five-angled point, the angles being formed by the slightly 

 raised ends of the spiral bands. In other cases, in the indigenous 

 Nitellas, for example, the side-walls of the enveloping tubes form a 

 greater portion of the shell, becoming broad, almost wing-like bands, 

 which are prominent not only at the sides but also at the ends of the 

 shell. In Chara frag His, C. harbata, and often also in C. foetida, the 

 lateral bands are not only strongly developed, but their part in the 

 formation of the cell extends itself over the angles in which the side- 

 walls of the five investing tubes with the basal turning-cell and the 

 nodal cell of the ovule buds meet, as also over the outer angles of the 

 cross-wall between the two last-mentioned cells. At the base of the 

 shell, therefore, answering to these five angles, there are five little 

 cloven feet, connected at the fissure by thin cross-bands, ^ which 

 moreover exhibit diff'erent degrees of perfection, according to 

 the individual. Further, the inner wall of the neckpiece of the 

 investing tubes elevated above the oospore, J and bordering on the 

 ovule-bud in the space below the crown, take a more or less extended 

 part in the formation of the shell, so that the five-angled crown is 

 overtopped by five erect prolongations, varying in size in each 

 diff'erent case. All these relations of parts may be observed in the 

 mature detached oospore, and their original base and crown dis- 

 tinguished with certainty. 



The structure of the ripe shell varies in different species, and 

 needs a more thorough comparative investigation. Suffice it here to 

 mention the following particulars. As already stated, it always pro- 

 ceeds, in the indigenous species, at least, from the persistent parts of 

 the enveloping membrane, and the outer walls especially are dis- 

 solved. 



In all species the shell consists chiefly of the densely packed, 

 from light to dark brown, parts of the membrane, which, from their 

 colour and great power of resisting the effects of destructive agents, 

 may be provisionally termed lignified, until further investigations 

 have determined the substances of which it is composed, and furnished 

 the clue to a more appropriate appellation. 



The colour of the lignified membrane differs usually according to 

 the species. In Tolypella intricata and Nitella mucronata it is a very 

 light translucent brown ; a darker brown in Chara foetida, Nitella 

 tenuissima, and allied species ; dark black brown to complete opacity 

 in C. fragilis, cotitraria, crituta, and scoparia. It appeared as if the 

 thickness of the membrane was in relative proportion to the intensity 

 of the colour, but no exact investigations on this point were insti- 

 tuted. For examining the earlier stages of germination the light- 

 coloured oospores, of course, are the most suitable ; and therefore it 

 is always better to choose the materials for investigation from among 

 the species bearing lighter-coloured oospores. Furthermore it 

 occasionally happens that a species with typically dark-coloured 

 oospores, C. crinitay for example, produces solitary, otherwise normal 



