Splachnidium rugosum. 9 



The sum of the characters of Splachnidium so expressly excludes it 

 from any existing natural order that there is no other course open to us 

 than to establish one for its reception under the name of Splachnidiacecz, 

 the main character of which shall be, reproduction by spores contained in 

 sporangia which are borne zcvV/^Vj conceptacles. It is possible that further 

 investigation of those genera of the Fucacece, about which little is at 

 present known, may lead to the discovery that such are really allied to 

 Splachnidium, and to their inclusion in the order. We may define this 

 order as follows, the subsidiary characters being necessarily provisional : 

 Splachnidiacece. Algae olivaceae, per fulcrum discoideum e fibris 

 radicalibus coalescentibus formatum, substrate affixse, frondibus ramosis, 

 externe e cellulis parenchymatibus interne e fills inter stratum mucosum 

 currentibus compositis. Sporse in sporangiis clavatis inclusae inter para- 

 nemata simplicia articulata in scaphidiis infra superficiem excavatis, per 

 totam frondem dispersis, collectae. 



Finally we wish to record our thanks to Mr. George Murray for 

 pointing out this research to us, and for his help and criticism during 

 the progress of our work. 



MARGARET O. MITCHELL 

 {Former Bathurst Student, Newnham College, Cambridge}. 



FRANCES G. WHITTING 



(Former Student of Newnham College, Cambridge). 



EXPLANATION OF PLATES. 



PLATE I. 



Fig. i. Mature plant of Splachnidium rugosum. Natural size. 

 Fig. 2. a. b. c. Mode of junction of some of the large filaments ( x 235). 

 Fig. 3. a. b. c. d. Large filaments not far from the apex, giving rise to small 

 lateral branches ( x 235). 



PLATE II. 



Fig. i. Transverse section of Thallus (x235). a. Epidermal layers, b. Cortical 

 layers, c. Filament. 



Fig. 2. Section of developing branch with its apical cell ( x 55). 



Fig. 3. Young filaments from near the apex ( x 235). 



Fig. 4. Section through the apex showing the apical cell with its basal process 

 and mucilaginous layers being shed externally, the apical hairs and the large fila- 

 ments in process of formation ( x 235). 



B 



