566 SUMMARY OF CURRENT RESEARCHES RELATING TO 



along a stem under atmospheric pressure, and then cutting sections to 

 ascertain the route followed by the solution. 



Germination of Ophioglossum.* — D. H. Campbell describes the 

 germination of the spores of Ophioglosmm moluccanum, 0. intermedium, 

 and 0. pendulum, and the earliest stages of growth up to the formation 

 of four, three, and thirteen cells respectively. 



Structure of Stolons of Nephrolepis.f — A. Sperlich describes the 

 function and behaviour of the stolons of Nephrolepis cordifolia, and 

 states that the secondary stolons are positively geotropic and throw out 

 roots, but may be converted into aerial stolons by decapitation of the 

 primary stolons. These secondary stolons he would style " wurzeltrager " 

 (root-bearers). The first rudiments of the stolons are formed at the 

 growing point, and many of them remain dormant. The roots also are 

 first traceable at the growing point in the initial layer, whence are 

 derived the parenchyma and endodermis. The structure of the aerial 

 and rooting stolons is similar, except that in the former the cortical 

 tissue retains its living condition to a distance of as much as some 

 decimetres behind the apex, being chlorophyllose, and provided with 

 intercellular spaces connected with stomata. The tough, elastic cha- 

 racter of the stolons is due to a sub-epidermal sheath of 6-7 layers of 

 lignified cells. The rooting and aerial stolons form a canal-system, 

 protected from crushing and from desiccation. The author compares 

 them with the rhizophores of Selaginella. 



Past History of Ferns. f — E. A. N. Arber discusses the past history 

 of the ferns in the light of recent discoveries, and sums up his main 

 results in a diagrammatic figure, which shows the geological periods 

 during which the Cycadophyta, Cycadofilices, Primofilices, Lepto- 

 sporangiatse, Hydropterideas, and Eusporangiatas, respectively attained 

 to the position of dominant factors. The name Primofilices is suggested 

 for the ancient stock from which the Mesozoic Leptosporangiatse were 

 derived. Recent research tends to show that the fern-like fructifications, 

 formerly regarded as belonging to the Eusporangiate ferns of Palaeozoic 

 times, are the male organs of Pteridosperms. Hence, it can no longer 

 be held that the Eusporangiatas were a dominant group in Palaeozoic 

 times, nor that they constitute a more primitive type than the Lepto- 

 sporangiatas. The Hydropterideaa are but doubtfully represented in 

 Mesozoic times, and hence are the youngest group considered in the 

 paper. 



Parichnos.§ — T. G. Hill discusses the presence of a parichnos in 

 recent plants. Having briefly summed up the results obtained in 

 Lepidodendron and other fossil plants by previous workers, he suggests 

 that the seeming discrepancies that are obvious in the various accounts 

 and figures may be explained simply by the view that the parichnos has 

 been preserved in different stages of development, varying from a definite 



* Ann. of Bot., xx. (1906) p. 321. 

 t Flora, xcvi. (1906) pp. 451-473 (2 pis.). 

 X Ann. of Bot., xx. (1906) pp. 215-32 (fig.). 

 § Tom. cit., pp. 267-73 (2 pis.). 



