288 Transactions. — Botany. 



Art. XXXV. — Note on Splachnidium rugosum, Grev. 



By Kobekt M. Laing, B.Sc. 



[Read before the Philosophical Institute of Canterbury, 2nd November, 



1892.'] 



This interesting plant is a brown seaweed common on the 

 coasts of both Islands, and growing a foot or two above low- 

 water mark. It seems to be an annual, as specimens of it are 

 very scarce during the winter months. It occurs" at the Cape 

 of Good Hope, and on the Australian coast, as well as in New 

 Zealand. It was first described by Linnaeus as Ulva rugosa ; 

 but the genus Splachnidium was afterwards founded for its 

 reception by Greville, and it still remains the only species of 

 the genus. 



It has hitherto been included in the order Fucacea, because 

 of its general external resemblance to them, and because it 

 has conceptacles which were supposed to contain oogonia 

 (v. " Phycologica Australica," plate xiv., Harvey). However, 

 in May, 1890, I was examining some specimens of this plant 

 which were lying in a saucer exposed to direct sunlight, when 

 I noticed a number of what I took to be oospheres entangled 

 amongst the hairs of aconceptacle near the top of the stem. I 

 mounted them on a slide with sea- water, and burst them by a 

 slight pressure. A large number of zoospores filled with 

 colouring-matter were at once extruded, showing that the 

 bodies in question were sporangia, and that previous observers 

 had been wrong in imagining them to be oospheres. The 

 zoospores were actively swimming in the water, and cilia were 

 distinctly visible on many. Most were egg-shaped, a few were 

 approximately circular, and an eye-spot was frequently discern- 

 ible. On another slide I obtained some which had come 

 to rest and thrown off their cilia — whether after conjugation or 

 not I cannot say. 



Since making these observations I have received a paper 

 entitled, " On Splachnidium rugosum, the Type of a New Order 

 of Algae,"* by Margaret O. Mitchell and Frances G. Whitting, 

 both of Newnham College. This contains an exhaustive de- 

 scription of the minute structure of the thallus and of the 

 mode of growth ; but the special feature of the paper is that 

 the authors have arrived by indirect evidence at the conclusion 

 that the bodies hitherto regarded as oogonia must be sporangia. 

 Their examination of the plant shows that in its vegetative 

 structure it is allied to some extent with the Fucacece {e.g., in 

 the possession of a conceptacle), but that on the other hand 



* Dulau and Co., Soho Square, London ; 1892. 



