(72) 



from the innermost of the large cells that form the middle stratum, and 

 consisting of a number of angular spores. Tetraspores formed from the 

 outer cells of the same stratum, pyriform, divided crossways into four 

 sporules. 



Until the beautiful analysis given in Plate 94 of Phyc. Brit, the 

 fructification of this common plant was but little known, and looked 

 upon as exceedingly rare, although it does not seem to be by any means 

 luicommon. The plant itself is common all round the British shores, 

 gi'owing at the sides and bottoms of pools between tides, extending a 

 little beyond low-water mark. In shallow pools it is short and stunted, 

 but in deeper water its fronds are long, slender, and brush-like, waving 

 gracefully in the swell as the tide ebbs and flows in its native pool. 



So closely allied both in structiu-e and external habit is this plant to 

 Polyides rotundus, that one almost feels a regret that the species should 

 be separated. The fructification, however, is so difi^erent that it has been 

 found necessary to place them in different families. 



From Polyides rotimdus it may be readily distinguished even in the 

 barren state by its fibrous not scutate roots, and the rather more acute 

 angles of the branches, which are generally more erect. 



When in fruit, the curious wart-like processes creeping over the 

 branches of Polyides rotundus will at once distinguish them with the 

 least chance of error. 



In making sections of this as well as of many other Algse, much 

 difficulty is often experienced in getting the section to lie flat for 

 microscopical examination. This is often very desirable when these are 

 intended for mounting as objects for the microscope, and can be readily 

 eflfected by the aid of gum arable, Canada Balsam, or some similar 

 substance, by which, when pressed down to the glass, they may be 

 retained in the desired position. 



EXPLANATION OF PLATE XCIII. 



1. — Furcellaria fastigiata, natural size. 



2. — Portion of frond with tips inflated. 



3. — Transverse section of rece^jtacle. 



4. — Longitudinal section of same. All magnified. 



