860 JOURNAL, BOMBAY NATURAL SISr. SOCIETY, Vol. XXIV. 



1^ cm. in diameter. Lobes linear oblong to obovate-oblong parallel, 

 closely attached to the substratum. Dorsal surface flat or slightly convex, 

 occasionally with a narrow middorsal groove. Ventral surface convex. 

 Transverse section elliptic or semi-circular ; midrib gradually passing into 

 the margins, wings practically absent. ThaUus compact. Scales absent. 

 Rhizoids only smooth, rarely a few with faint tubercles. Antheridia 

 oblong cylindrical in one or two rows. Archegonia indicated in the young 

 state sometimes by a red spot on the dorsal side, neck not projecting out- 

 wards. Sporogonia in one median row on each lobe, distant, dehiscing by the 

 rupture of the dorsal tissue. Spores opaque tetrahedral, 50u., granular 

 or with very close, irregular, almost wavy streaks. 



Habitat. — Extremely common on the banks of the Ravi in Lahore. Also 

 found at Banda on the banks of the Ken. Of the three species of Riccia 

 found in Lahore, it is the first to appear in the beginning of winter and the 

 last to disappear, lasting from about September to about April. 



A comparative study of the species of the genus Riccia described 

 above confirms the view as to the origin of forms like Riccia from some 

 Targionia — like ancestor, expressed by the writer in the New Phytologist 

 (Vol. XIII, No. 9, page 317, and Vol. XIV, No. 1, page 1). Riccia pathan- 

 kotensis is especially interesting in this connection. In deriving this genus 

 from some Targionia-Yike form we should have the continued growth of the 

 thallus forward, so that the involucre becomes dorsal and later on the 

 gradual elimination of the involucre itself. An illustration of the first step 

 we find in the genus Cyathodium (Lang ; The morphology of Cyathodium. 

 Annals of Botany, 1905). In most species of this genus the involucre is 

 ventral and the archegonia apparently on the ventral surface which, how- 

 ever, is really the dorsal surface. In C. cavernarum, the archegonia lie 

 actually on the dorsal surface. The next step would be a little further 

 growth of the thallus and reduction of the involucre so that the archegonia 

 would then lie in a broad channel as is actually the case in Riccia pathan- 

 kotensis and some other species. Targionia has already developed vegetative 

 tissue between its antheridia. Riccia has gone further and formed it 

 between the archegonia as well. According to this view those species which 

 have no trace of a dorsal channel would be the most reduced, e.g., R. 

 sanguinea. This is. confirmed by the absence of scales and tuberculate 

 rhizoids in this last species. At the same time the structure of the thallus 

 of the species put in the section Ricciella resembles that of the thallus of 

 Cotsinia, &c., and it is possible therefore that the genus Riccia has really 

 originated from two different sources. 



