272 THE SPORE-PRODUCING ORGANS [ch.xiii 



218. Scott. Studies in Fossil Botany. 5rd Edn. Vol. i, p. 366, etc. (1920). 



219. Russow. Vergleichende Untersuchungen. St Petersburg, 1872, p. 86, etc. Here 

 the first comparison of spore-numbers is to be found. 



220. Hannig. Ueber die Bedeutung der Periplasmodien. Flora. Vol. 102, p. 243. 



221. Hannig. Ueber das Vorkommen der Periplasmodien bei den Filicineen. Flora. 

 Vol. 103, p. 321 (with full references). 



222. Strasburger. Ueber a so/la. Leipzig. 1875. 



223. Prantl. Die Hymenophyllaceen. Leipzig. 1875. 



224. Prantl. Die Schizaeaceen. Leipzig. 1881. 



225. Thompson. Stromatopteris. Trans. Roy. Soc. Edin. Vol. lii, p. 133. 1917. 



226. Thompson. Platyzoma. Trans. Roy. Soc. Edin. Vol. li, p. 631. 1916. 



227. Thompson. Further. ..on Platyzoma. Trans. Roy. Soc. Edin. Vol. lii, p. 157. 1917. 



228. Yamanouchi. Sporogenesis in Nephrodium. Bot. Gaz. xlx, p. i. Here full refer- 

 ences are given to cytological literature. 



229. LuERSSEN. Rab. Krypt. Flora, Vol. iii. Farnpflanzen, passitn. 



