214 Cavers: So7ne Points in the Biology of Hepaticce. 



matting', sometimes hanging- downwards as festoons. In these 

 forms either the whole leaf or a part of it is converted into 

 a sac or pitcher in which water is stored. This may be effected 

 by the whole leaf becoming- folded long-itudinally, so as to 

 resemble the valves of a mussel-shell (e.g-. , Mytilopsis), or 

 becoming- dilated at the base (e.g-. , Nowellia CTirvifolia) ; or the 

 lower lobe of the leaf is sharply bent on the upper (e.g". , Scapania, 

 Radula, PorelLa, most Lejeuneae). In Frnllania and Pleurozia 

 the lower lobe of the leaf is modified to form a hemispherical or 

 cylindrical sac (Fig". 12) ; in Lepidolcena sacs of this kind are 

 borne both on the lateral and the ventral leaves (amphig-astria), 

 and in Coliirolejeiinea the whole leaf is converted into a pitcher. 

 In Pleurosia and Colurolejeiinea the opening- into the cavity of 

 the sac is g-uarded by a valve which readily opens inwards but 

 not outwards, and as the remains of small animals (rotifers, 

 Crustacea, insect-larvae) are sometimes found in the pitchers, it 

 has been sug"g"ested that these liverworts resemble in miniature 

 the well-known insectivorous 'pitcher-plants.' In many of the 

 leafy Jung'ermanniales the rhizoids are found to be traversed 



by fungfal hyphae, 

 which pass into the 

 lower cells of the 

 stem, forming- a 

 mycorhiza com- 

 parable with that 

 found in various 

 thalloid Hepaticse 

 (e.g., Fegatellay 

 Preissia). 



\n interesting 

 but somewhat 

 obscure feature in 

 the biology of the 

 Hepaticse is the 

 presence of iVos/oc- 

 colonies in their tissues. Chains of this blue-g"reen Alg"a are 

 frequently observed in the cells of the compact ventral tissue of 

 the Marchantiales, whilst in Blasia and the Anthoceroteae they 

 are found inhabiting special organs. In Blasia these organs 

 have the form of hollow spherical outgrowths, from the lower sur- 

 face of the broad stem, two of these ' auricles ' usually occurring 

 at the base of each leaf; in the Anthoceroteae the Nostoc-co\on\<is 

 are contained within special chambers in the tissue of the host- 

 Naturalist, 



FJg. 12. — Two species oi Prullanla f ventral views showing: 

 the three rows of leaves, the lateral ones bearing' pitchers. 

 X 40. 



