THE PAST HISTORY OF MONOCOTYLEDONS 1 75 



Several fossils giving the name to a series of beds of Tertiary age 

 are assigned to Pistia — a tropical aquatic plant, like Lemna — in 

 North America. Of these P. corrugata, Lesqx., from the Point of 

 Rocks, may rightly belong to this genus, and the fossil called Ottelia 

 a/neriama, by Lesquereux, also ; whilst Lemna scutata, described by 

 Dawson, aiJpears to be a young plant, and what is regarded as a 

 parallel nerve at the margin is perhaps a fold, the whole leaf being 

 much compressed. 



The oldest forms referred to Pistia, P. mazellii. Sap. and Mar., 

 are from the Upper Cretaceous of Bouches-du-Rhone, near Faveau, 

 and are allied -like P. corrugata — to the recent P. siraiiotes, L. Of 

 the fossils from the chalk of Senden, referred to this genus or allied 

 forms, some may be cycads others dicotyledons. The fossils placed 

 in Pistitea and Lenviophyllum must be excluded according to 

 Schenk. 



xiii. LemnacecB. 



Of fossil Lemnas there are few which are founded on any solid 

 basis. From the Tertiary of Wurtemberg Probst describes a form, and 

 Lesquereux founds a species, Lemna penicillata, upon material from 

 the American Oligocene, and the genus is cited from the Miocene 

 of Wurtemberg. 



V. FARINOSiE. 



XV. EriocaulacecB. 



The anomalous distribution of Eriocanloji septatigu/are, which is 

 an /American plant with a single European station or stations in the 

 Hebrides, Isle of Skye, is perhaps elucidated by the occurrence in 

 Tertiary rocks, at Sand Creek, of a fossil named Eriocaulon {})porosum, 

 by Leo. Lesquereux, and, as pointed out by Schimper and Schenk,^ 

 suggests a former connection between Europe and North America 

 in Tertiary times, whilst the former connection between Japan and 

 North America may be suggested by the occurrence of Eriocaulon 

 sexangulare in both of those countries, but not elsewhere. 



Dr. Rendle remarks upon the distribution oi E. septangulare. " This 

 species also occurs in Atlantic North America, and like Naias flexilis 

 and Sisyrinchium angtistifolium indicates a former closer relationship 

 than at present obtains between the north temperate floras on the 

 two sides of the Atlantic.'"^ 



xvi. Co//iJ/ieIinace(Z. 



Certain fossils described by Caspary with flowers with 3 sepals, 

 3 petals, and 6 stamens, from the amber of Samland, as Cotn- 

 me/inacites dic/ioresa?idroides, may be referred provisionally to Com- 

 melinaceas, and Maianthe77iophylliivi contains species which resemble 

 them in leaf-form. 



^ ''Traitede paleophytologic," 1891, p. 355. 

 ^ "The Classification of Flowering Plants," vol, i., 1904, p. 274. 

 VOL. L 13 



