1886-87.] Mr E. M. Holmes on Sphacelaria radicans. 81 



in scattered tufts. In Sphacelaria trihuloidcs, however, 

 which I met with at Dunbar, the joints are twice as long 

 as broad.) The felted mode of growth of S. olivacea, Dillw., 

 and the diameter of the filaments, which is only about half 

 of that of aS'. radicans, Dillw., and the growth in small 

 isolated tufts of S. raceinosa, and the racemose fruits, are 

 the best modes of distinguishing the species from >S'. radicans, 

 Dillw. 



Pringsheim {Morphol. Differenzirung in der Sphacelarieen- 

 Rcihc, Berlin, 1873, p. 165) has given the best description yet 

 published of the fructification of S. olivacea.^ He figures 

 the following reproductive organs : — 



1. Unilocular sporangia, of an elliptical or oval form, ter- 

 minal on pedicels, consistmg of about three joints. 



2. Globular sporangia, on longer stalks, consisting of about 

 nine joints. (These appear to be plurilocular sporangia.) 



3. Propagula, or deciduous special branches, like those 

 found in S. cirrhosa. 



4. Gemmffi (Brutzellen), formed out of lateral segments 

 of the joints, which may either develop into ordinary or into 

 fruit-bearing ramuli, or subdivide and form a conglomera- 

 tion of cells on the branch. 



The sessile bodies, figured in the Phycologia Britannica 

 as the fructification of S. radicans, are considered by Pring- 

 sheim to be probably a parasite, similar in character to, but 

 different from, Chytridium. 



With respect to the time of fructification, he remarks that 

 the germination of the zoospores often takes place very 

 slowly, since he has found sporangia in July and August, 

 with spores but little advanced in development (I have found 

 them in August). The plurilocular sporangia were also met 

 with in July and August. 



The deciduous special ramuli, or propagula, he found of 

 rare occurrence, except in a solitary tuft, which was remark- 

 able for the abundance of hairs it bore. 



On the cfespitose form of the plant the propagula appeared 

 to be extremely rare, and they were developed out of the 

 gemmai above alluded to. 



Pringsheim's statement concerning the sessile fructification 



* Pringsheim recognises four varieties of S. olivacea, Dillw., viz., caspitosa, 

 radicans, solitaria, and clatia. 



TRANS. BOT. SOC. VOL. XVII. F 



