ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 733 



CRYPTOGAMS. 



Pteridophyta. 



(By A. Gepp, M.A., P.L.S.) 



Ancestry of Plants.* — A. Meyer publishes a hypothesis about the 

 vegetative ancestry of the Pteridophytes, Gymnosperrns, Angiosperms, and 

 Brvophytes. He calls attention to the remarkable gaps which occur in 

 the continuity of the vegetation which runs through the successive geo- 

 logical strata, the absence of any interesting remains in the Cambrian, 

 and the lack of connecting links between the remains of the great groups 

 of the Angiosperms, Gymnosperrns, Lepidodendracere, Mosses, etc. It is 

 astonishing that the Cambrian, which produced so many animals, should 

 not have preserved adequate remains of its plants. The sudden appear- 

 ance of the well-developed Lepidodendraces, Calarnariacese, and the 

 Cycadofilices in the Silurian and Devonian is very striking ; so also the 

 sudden appearance of the Angiosperms in the Cretaceous. Meyer does 

 not believe in the theory that the connecting links have not been pre- 

 served. His hypothesis is that practically all our modern vegetation 

 arose from a group of small plants, so tender and so fragile that though 

 they lived up to Cretaceous times, yet very little if anything of them 

 has been preserved. This group arose perhaps in Cambrian times from 

 fresh-water algaa, and differentiated itself (as shown in a diagrammatic 

 table) into sub-groups. In appearance it resembled the prothallia of 

 ferns and the gametophytes of the mosses ; it did not develop a sporo- 

 phyte, but only a spore or sporangium, which gave rise directly to similar 

 individuals. By gradual development and differentiation the various 

 groups budded off from the primitive stock. The Cambrian flora was 

 entirely marine, and then gradually came the formation of land and of 

 fresh-water. He works out his hypothesis in detail. 



Sex of Gametophyte of Onoclea.f — D. M. Mottier publishes some 

 notes on the sex of the gametophyte of Onoclea Struthiopteris. The 

 results of his very careful examination of innumerable plants are as 

 follows. 1. The spores of 0. Struthiopteris when grown upon earth, 

 under optimum cultural conditions, produce regularly three kinds of 

 prothallia : (a) small plants bearing only antheridia, the so-called male 

 gametophytes ; (b) larger prothallia bearing only archegonia, the female 

 gametophytes ; (c) those bearing both archegonia and antheridia, the 

 bisexual or monoecious prothallia. 2. Archegonial prothallia, which 

 continue growth without bearing a sporophyte, sometimes develop 

 numerous small lobes from the older portions upon which numerous 

 antheridia appear. 3. The gametophyte, therefore, is not strictly di- 

 oecious, and there is in all probability no sex-determining chromosome. 

 4. It is highly probable that the development of purely male or female 

 gametophytes is not dependent upon conditions of nutrition, but that 

 the sexual tendency is predetermined in the spore. Environmental con- 

 ditions, or the failure of an egg to give rise to a sporophyte, owing to 

 a lack of fecundation, may induce the development of antheridia upon 



* Ber. Deutsch. Bot.Gesell., xxviii. (1910) pp. 303-19 (fig.). 

 t Bot. Gaz., 1. (1910) pp. 209-13. 



