66 SUMMARY OF CURRENT RESEARCHES RELATING TO 



General. 



Pleistocene Flora of Canada.* — D. P. Penhallow has examined 

 various leaves from the interglacial deposits of the Don Valley, Toronto. 

 The specimens included Acer pleistocenicum, A. torontoniensis, Garya 

 alba, Gercis canadensis, Gyperus sp., Gleditschia donensis, Madura auran- 

 tiaca, Picea nigra, Ostrija virginica, Platanus occidentalis, Populus 

 grandidentata, Primus sp., Quercus alba, Robinia pseudacacia, Tilia 

 americana, and Ulmus americana. The present examination confirms 

 previous conclusions as to the Don flora, and the existence of a climate 

 warmer than the present one. It is now definitely proved that succes- 

 sive northerly and southerly movements of the continental ice-sheet 

 involved corresponding movements in the vegetation, and brought about 

 the elimination of unstable species. The evidence of the Pleistocene 

 clays of Toronto agrees with that of similar deposits at Elmira, New 

 York, etc. 



Affinities of the Chicoracese.f — L. Dufour has studied the cotyle- 

 dons of this group with special reference to its evolution and affinity. 

 There are two distinct types of cotyledons ; those of the first group are 

 broad, but they rarely exceed 20 mm. in length, while the petiole is 

 often ill-defined. This type of cotyledon is characteristic of Gichorium, 

 Lactuca, Sonchus, Grepis, Taraxacum, Hieracium, etc. The second type 

 is less common, but is found in the genera Scorzonera, Tragopogon, 

 Geropogon, and Podospermum ; here the cotyledons often reach a length 

 of 50-60 mm., while the breadth does not exceed 3 mm. The author 

 regards the present classification of the Chicoraceae as very artificial, 

 and suggests that they should be divided into two groups according to 

 the characters of their cotyledons. One group should comprise such 

 types as Tragopogon, etc., the simplest being Scorzonera and Tragopogon, 

 with undivided leaves, while Podospermum, with its much-divided leaves, 

 is the most highly evolved type. The other group should comprise 

 Gichorium, Lactuca, etc., and here, again, there is a gradual transition 

 from the simple to the much-divided leaf. 



Both groups appear to have had a common origin in plants with 

 simple leaves, and this character is frequently revealed in the cotyledons 

 and first foliage leaves. 



Monograph of the Genus Ribes.} — Ed. de Jancewski has published 

 an exhaustive account of this genus, in which he includes as a section, 

 as is now usually done, Grossularia, to which belongs the gooseberry. 

 The genus contains 133 species, for most of which a figure of the flower 

 is given in addition to a very full description of the plant. 



Harmful Secretion of Sugar in Myrmecophilous Plants.§ — M. 

 Nieuwenhuis von Uexkull-Giildenband has studied myrmecophilous 

 plants, in order to test the opinion of Delpino, Kerner, and others, that 

 the secretion of sugar in extra-floral nectaries, is useful in attracting 



* Amer. Nat., xli. (1907) pp. 443-52 (2 figs.), 

 t Comptes Rendus. cxlv. (1907) pp. 567-70. 



% Mem. Soc. Phys. Hist. Nat. Geneve, xxxv. (1907) pp. 199-517 (202 figs, in 

 text). § Proc. Acad. Amsterdam, ix. pt. 1 (1907) pp. 150-6. 



