Spiachnidium rugosum. 7 



The reproductive organs here described are the only ones which have 

 been found in Spiachnidium rugosum ; and there are before us three 

 possible interpretations of these organs : 



i. That they may be oogonia containing a very large number of small 

 oospheres. 



2. That they may be large antheridia. 



3. That they may be sporangia like those of the Laminariacecs containing 

 zoospores. 



We will proceed to a consideration of each of those possibilities. In 

 connexion with the first we must note that Mr. R. M. Laing, in the paper 

 cited above, refers to these organs in the following words : ' The con- 

 ceptacle is surmounted by a ring of hairs, and in its interior contains a 

 number of unbranched hairs. The oogonia are obscurely pedicelled and 

 developed in the cells lining the wall of the cavity. Each oogonium gives 

 rise to a large number of oospheres, thus differing from all the other 

 Fucacecz that have hitherto been described. Each oosphere is very small 

 compared with the oospheres of any of the other Fucacea? A rough figure 

 (op. cit., plate X., fig. 7) accompanies this note, and it is apparent that the 

 author has anticipated the view that these bodies are oogonia with numerous 

 minute oospheres. Harvey* also regarded them as oogonia. Mr. Laing, 

 believing these bodies to be oogonia, and failing to find antheridia 

 developed as in typical Fucacece, suggests, as has been already said 

 that the antheridia are to be found in the peculiarly shaped hairs which 

 cover the apex of each branch ; that these are merely hairs has been 

 already shown. 



That the sporangia of Spiachnidium rugosum, however, are not oogonia 

 homologous with those of the Fucacece appears obvious from the following 

 facts : 



1. The enormous number of the spores (500-600), as compared with 

 the largest number of oospheres in an oogonium of the Fucacea, i.e., 

 eight. 



2. The small size of the spores, the bulk of an oosphere of the Fucacecs 

 being 20,000-30,000 times as great. Though deprecating size as an im- 

 portant characteristic, surely there is here a sufficiently wide margin to 

 entitle us to base an argument upon it. 



3. The absence of a pedicel cell. 



4. The absence of an inner membrane within the wall of the sporangium. 



Secondly, that they are not antheridia homologous with those of the 

 Fucacecs appears plain from the following facts : 



* Harvey. Fhycologia Austrcilica, vol. i. 



