318 SUMMARY OF CURRENT RESEARCHES RELATING TO 



Graft-hybrids.— F. La Marca {Compf. Rend., 1918, 166, 647-6i9). 

 A note upon a new graft-hybrid ; the graft is the GannelUna variety of 

 the olive-tree, while the stock belongs to the Gaiazzana variety. The 

 writer found three such grafted trees which produced black fruits similar 

 to those belonging to the stock, and white fruits like those of the graft. 

 Further investigation showed that the kernels of the fruits, both in form 

 and marking, were intermediate between the graft and the hybrid. The 

 peduncles and leaves were also intermediate in character. Analysis of 

 small quantities of oil taken from the hybrid showed that in acidity, 

 and in its behaviour under the influence of light and air, this oil differs 

 from that extracted both from the stock and the graft. The observa- 

 tions extended over four years, and may be regarded as confirming the 

 opinion of those writers who support the theory of asexual hybridization. 



S. G. 



CRYPTOGAMS. 



Pteridophyta. 

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



Study of Some New Cases of Apog^amy in Ferns.— W. N. Steil 

 {Bull. Torrey Bot. Club, 1918, 45, 98-108, 2 pis.). During the past 

 six years the author has discovered apogamy in many ferns, especially in 

 PeUsea, Pteris, Aspidium. In a summary of his results he states that 

 the material was grown under cultural conditions favourable for the 

 development of sex-organs and embryos in non-apogamous species. The 

 apogamous prothallia became heart-shaped before producing the embryo, 

 and bore antheridia, but rarely archegonia. The embryo usually appears 

 as a compact region of cells posterior to the apical notch and on the 

 ventral side of the prothallium ; and in several species tracheids are 

 visible in the pale portion of the gametophyte. First appears the apical 

 cell of the leaf, then that of the root, and later that of the stem ; but so 

 far no foot has been observed in an apogamous embryo. Either root or 

 leaf or both may develop on the dorsal side of the prothallium, but as a 

 rule arise on the ventral side. As a rule the embryo is produced behind 

 the apical notch, but may be formed on a cylindrical or conical 

 "process," and occasionally on the lobes of the prothallium. Several 

 apogamous embryos may be formed on a single prothallium. Secondary 

 prothallia are readily produced (just as in non-apogamous species), and 

 these form embryos like those of the ordinary prothallia. The " light " 

 area present on some apogamous prothallia is rendered more conspicuous 

 in cultures maintained in weak light ; also the conical or cylindrical 

 " process " increases considerably in length when the prothallia are 

 grown under these conditions ; and, further, the embryo often arises 

 directly from the apical region of the prothallium in weak light. In 

 the case of Osmunda regalis, prothallia cultivated in strong light and 

 prevented from fertilization for a year and a half failed to produce 

 apogamous embryos. A. G. 



Comparative List of Fern Pinna-traces, with some Notes on 

 the Leaf-trace in the Ferns. — E. C. Davie {Annals of Botany, 1918, 

 32, 233-245, figs.). The author gives a complete tabular list of all the 



