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70 REVUE BRYOLOGIQl'E 



I 



A. — Male plant, X l- B. Female plant, X 1- C. Female plant, in which three 



capsules are exserted, X •■ D Ripe capsule, showing dehiscence by 

 a single longitudinal slit, X 5. E. The same, later; the margins have 

 rolled back, exposing the mass of spores and elaters ; X ^- 



^ ■ 



The genus Monoclea ivS represeuLed by two species, M. Forsleri^ 

 which occurs in New Zealand and in Patag)nia, and ^[. Gollschei 

 Lindb., which has a somewhat wider distribution, occurring in 

 various parts of Central and Sputh America and in Japan. 



The writer's examination of large numbers of living plants 

 (New Zealand form, kindly sent by Mr. George Webster, of York) 

 has brouglit to liglit several points in the structure and develop- 

 ment of Monoclea which appear to have escaped the notice of 

 previous observers. 



The broad creeping thallus, wliich often reaclu^.s a length of 

 about 12 cm. and a breadth of 2,3 cm., shows fairly regular 

 dichotomous braching and is attached to the soil by numerous 

 rhizoids which spring from its ventral surface (Fig. 1), The upper 

 surface of the thallus is quite smooth, and the plant has the gene- 

 ral habit of a Large Pellia. there is no distinct midrib, the thallus 

 being about ten cells thick in the middle and gradually thinning 

 out to a single or double layer of cells at the margin. The super- 

 ficial cells on both the upper and the lower surface of the thallus 

 are distinguished from the internal cells by their small size and 

 nearly cubical form. The cells of the dorsal superficial layer (epi- 

 dermis) contain numerous small chloroplasls, which are also found 

 in smaller quantity in the underlying cells- (Fig. 2 D.). A strikin 

 feature in the thallus, when examined in surface view under a low 

 power, is the presence of great numbers of large oil-bodies, sphe- 

 rical or ovoid in form and dark brown in colour. These bodies are 

 larger than any which the writer has observed in the tissues of the 

 Marchantiacca), and sometimes reach a diameter of nearly 0,1 mm. 

 Each of the oil-bodies is contained in a cell, which it nearly fills. 

 These cells are S!^en in seclionsof the thallus to occur chiefly in two 

 layers, one of which lies immediately bciow the dorsal epidermis, 

 the other immediately above the ventral epidermis (Fig. 2. A. D.). 

 On treatment with alcohol the oil-boLHes rapiiliy become dissol- 

 ved, so that in spirit-preserved specimens they can no longer be 

 observed. When a section of the thallus is irrigated with alcohol, 

 and an oiUbody is kept under observation, it is found that the 

 oil-body first loses its brown colour and a number ofhiglily refrac- 

 tive drops become visible. These drops soon run together and then 

 disappear, but there remains a delicate envelope which retains 

 the outline of the oil-body, though undergoing some contraction. 





