GEAF ZU SOLMS-LAUBACH— MONOGRAPH OF TJIE ACETABULAlllE.i:. 17 



long after the commencement of the growing out of their hairs, divides its(^ll' into 

 sporangial ray and corona inferior. It is impossible to close one's eyes to the view that 

 the whole chamber with all its parts represents a complete formation, if, indeed, one may 

 not take it as the homolosrue of a sincrle whorl. That this mav be so I believe I am in a 

 position to prove. It is common to all Dasycladecc that the branching of their short 

 shoots is of the di-polychotomous type, and to this rule the AcetabulariecB, as regards 

 their sterile branches, form in no way an exception. As regards the morphological 

 position of the sporangia, there are two actually diiferent cases, if we look away from 

 Acetahularia and its allies. The one occurs among the CymopoliofP, the other among the 

 Bornetellece. In the former case the sporangium arises from the apex of the ray whicli 

 has already produced its branch-whorl, if such there be ; and this teaches us that we 

 have to do with a cymose and not with a dichotomous or polychotomous system in the 

 branching of the short shoot. In Dasycladus, Neomeris, and Cymopolia it is the 

 primary shoot which terminates in a sporangium ; in Botryophora secondary branches 

 take part also in this transformation, but these have no farther branching. There thus 

 arise lateral as well as terminal sporangia, but these belong to the branch-whorl itself 

 and are homologous with the secondary rays. It is quite otherwise in Bornetella. Here 

 the sporangia occur as lateral outgrowths in indefinite numbers and position from the 

 primary ray, whicli ends blind in all cases after it has given rise to the characteristic 

 whorl of secondary rays forming the rind. The sporangia of Bornetella are lateral new 

 formations, and they should not be compared with the parts of the normal branching 

 system. 



How, then, do the sporangial rays c>{ Acetahularia compare Avith this ? I do not hesitate 

 to assert that they could be compared only wnth tliose of Bornetella. In Acetahularia 

 polyphysoides, for example, or A. 3Idbii, the basal part, together with the coronal promi- 

 nences it bears, is equivalent to the basal part of the short shoot ; the crown of hairs on 

 the terminal prominences is the whorl of the secondary branches. It is plain that the 

 sporangial ray does not belong to this wiiorl — it is a protuberance of the basal portion 

 that is only apparently pressed into a terminal position. It is distinguished from the 

 sporangium of Bornetella by its aberrant form, by its occurrence singly, and by its 

 definite position on the basiscopic side of the branch. But these relations are not so 

 clear in all Acetahularieoi as they are here. In the section Bolypliysa, which affords 

 simpler relations of organization, and in SaUeoryne and Chalmama as well, there is 

 present a manifest limit between sporangium and basal portion ; in Acicularia, Acetabu- 

 loides, and Acetabulum these become somewliat obliterated. And at the same time the 

 Avreath-like position of the secondary branches on the single sections of the corona 

 becomes less clear, until finally, in many species of Acetabuloides and Acetabulum, they 

 come together in a radius forming a single row. The most aberrant type is Acetahularia 

 viediterranea, for long the only one closely studied, in which the closed connection of the 

 parts is found. 



With this statement the course of development is in accord. The apex of the ray. th(^ 

 corona with its hairs, is formed much earlier than the sporangium and may be regarded 

 at first— at least wdth as much justification as the other- as the terminal portion of the 



SECO^•D SEHIES. — BOTANY, VOL. V. ^ 



