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60 _ REVUE BRYOLOGIQUE | 
of the branches grow out into long and $lender flagella, the antical 
… lobe of the leaves is undivided or bifid, and the leaf-margins are 
_ entire or dentate but never truly ciliate. These differential charac- 
ters are certainly less definite than might be desired. If, however, 
both genera are recognized, the Japanese species is a Plilidium 
rather than a Mastigophora, because of its blunt branches and 
_ also because of its mullifid leaves with marginal cilia. 
Water-sacs and cilia increase the capacity of a species for 
… absorbing and retaining water. The water-sac is a structure which 
is found in many genera of the leafy Hepaticae. Aside from the 
. vast tribe of the Jubuleae, where it is of almost universal occur- 
rence, it has been described as a constant or occasional character 
in the genera ARadulu, Ascidiota (1),-Lepidolaena, Hariotiellu (4), 
Cephalozia (Nowellia), and Plagiochila (2), as well as for Ptili- 
_ dium as described above. In certain species, although normally 
_ present, it fails to develop when the plants are exposed to an 
= excess of moisture. Wherever it occurs the water-sac represents a 
peculiar modification of a part of a leaf, sometimes involving the 
whole of one of (he principal lobes, sometimes a portion only of 
such a lobe. es. : 
When hairs or cilia are present on the leaves they are usually 
restricted to the margin. Surface-cilia have been described for 
very few species. In SCnISTOCHILA GLAUCESCENS (Hook.) comb. 
nov. (3), of New Zealand (1), they apparently reach their highest 
development, being not only multicellular but also copiously 
branched. Some of these compound hairs arise directly from the 
leaf-cells, others are borne on the margins of narrow and inter- 
rupted surface-lamellae, similar to those found in other members 
of this same genus, In Ptilidium Bisseli the cilia, although un- 
branched, are still multicellular; but in the majority of the cases, 
which have been described, the cilia or hairs are simply protube- 
__ rances from the surface-cells. This, for example, is the case with 
 Cololejeunea venustu (S.-L.) Schiffn. (4), of Java. From hairs © 
this character it is but a step to the conical or sphaeroidal projec- 
tions from the leaf-cells which are found in so many of the 
_ Lejeuneae. Ru res es 
Yale University. New-Haven, Connecticut. 
co 
(1} Massalongo, Nuovo Gior. Bot. Ital. (Nuova Seric; B: 255-960. pl. 2. 180. 
_  (@) For example, P. mutabilis De Not. Mem. Accad. Sci. Torino, IL 
28 : 279, PI. 8. 1874. à hs ne 
(3) Jungermannia glaucesvens Hook. Musc. Exot. pl. 39, 1818. Gottsc 
 glaucescens Nees; G. L. et N. Syn. Hep. 90. 1844. a nie 
© Engler et Prantl, Nat, Pflanzenfam. 45 : 422. 1893. Lejeunea venust 
Syn. ep Jav. 64. pl. 12. 1856. 
