GROUP 11. BRYOPHYTA : HEPATIC^. 847 



In some of the foliose Anacrogynse (Fossombronia, Androcryphia, Petalo- 

 phyllum) the development of the leaves is essentially similar to that of the 

 lateral leaves of the Acrogynae ; but in none of the Anacrogynae is the leaf 

 bilobed. In Haplomitrium each segment gives rise to a leaf which is developed 

 in the same manner as those of the Mosses : in Eiella each segment gives rise 

 to two leaves : in Blasia there are two rows of lateral leaves and two rows of 

 amphigastria. 



In some epiphytic forms (e.g. Frullania) the lower lobe is somewhat cup- 

 shaped (Fig. 245), and is termed an auricula; it constitutes a receptacle for 

 water. In some, also, (e.g. Frullania, Lejeunia, Scapania), the upper lobes of 

 the leaves of male fertile shoots are modified to constitute protective organs for 

 the antheridia. 



The leaf-formation of Blasia is quite peculiar, especially in this respect, that 

 the first development of the lateral leaves takes place in the same plane as that 

 of the stem, with a subsequent slight obliquity, so that the leaves are incubous. 

 Each lateral leaf bears at its base, on the under surface, two (sometimes only 

 one) appendages which are termed auriculae but are not morphologically similar 

 to the auriculae mentioned above as occurring in Frullania. The auricula of 

 Blasia consists of a cellular wall enclosing a cavity, with a narrow apical aper- 

 ture, from the centre of the floor of which there springs a glandular hair 

 secreting mucilage. Into this cavity filaments of Nostoc (see p. 234) make their 

 way, so that it becomes filled with a mass of this Alga. The hair then grows 

 out into a number of branches, resembling root -hairs, which ramify in the mass. 

 This symbiosis (see p. 273) appears to be advantageous both to the Nostoc and 

 to the Blasia. An auricula which does not become infested with Nostoc re- 

 mains relatively small. The amphigastria of Blasia are stalked and peltate ; 

 they bear a glandular hair which is situated at first on the margin of tbe am- 

 phigastrium at the apex, becoming gradually displaced until its insertion is at 

 the centre of the free surface. 



The sexual organs are generally borne on the main axis and its normal 

 branches, but in many cases (e.g. Metzgeria, Mastigobryum, Calypogeia, 

 Lepidozia, Saccogyna, Lophocolea, many species of Jungermannia) they are 

 confined to more or less specialised ventral branches (gametophores). The 

 place of development of the archegonia affords the basis for the classification 

 of the Jungermanniaceae into the two main groups, Acrogynae and Anacrogynae. 

 In the former, which includes all the foliose forms (except Blasia, Fossombronia, 

 Androcryphia, Petalophyllum, Haplomitrium, Eiella), the archegonia are pro- 

 duced from the apical cell and its youngest segments at the growing-poiut ; 

 hence when the formation of the archegonia takes place on a shoot its further 

 elongation is arrested. In the latter group, which includes all the thalloid 

 forms and the exceptional foliose forms just mentioned, the archegonia are 

 produced laterally, on the dorsal surface in the dorsiventral forms, on all sides 

 in the radial forms (species of Biella, Haplomitrium) ; hence the growth in 

 length of the shoot is not necessarily arrested. 



The archegonia of the Acrogynaa ara borne either singly (Lejeuuia, Phrag- 

 micoma), or in groups of two (Frullania) or more (e.g. Kadula, Alicularia, 

 Lophocolea). Each archegonium is developed from a single cell ; when the 

 archegonium is single it is developed from the apical cell; when there are 



