242 SUMMARY OF CURRENT RESEARCHES RELATING TO 



Sclerenchymatous Cells in the Flesh of the Pear.* — According to 

 Herr H. Potonie, the sclerenchymatous cells which, in the cultivated 

 pear, are scattered through the flesh, lie, in the wild forms, in a closed 

 very hard zone surrounding the core; and he regards them as the 

 remains of a shell which, in the ancestors of the present species, 

 inclosed the seeds, as is now the case with the medlar and with many 

 species of Crataegus. The same applies also to the quince and to some 

 Oleaceaa. 



Development of Cork- wings. f — Miss E. L. Gregory now describes 

 the development of cork-wings in certain species of the genus Euonymus. 

 The first important consideration on taking up the study of the wing in 

 this genus is, that we have no longer to do with large trees, but with 

 small trees and shrubs. Of the thirteen species of Euonymus examined, 

 five may be said to be winged, and of these E. alatus, formerly described 

 as Celastrus alatus Thb., presents the most marked and striking example. 

 In this species there are four sharp thin wings extending along the 

 internodes, not at the corners, but as nearly as may be exactly between 

 them. The formation of the wing takes place ordinarily after the 

 internode has reached its full length. The first indication of it externally 

 is a little line of brown flecks at equal distances from the ridges at the 

 corners. The author concludes by stating that the periderm does not 

 originate from the epidermal cells, if by periderm is meant the corky 

 growth covering older stems, but from certain layers of cells at a greater 

 or less distance below the epiderm. The cells which are cut off from 

 the epidermal layer form an additional support to the outer collen- 

 chymatous cylinder which at first is only two layers in thickness. By 

 means of these additional cells from the epiderm the number of layers 

 is often increased to six or seven. 



Bordered Pits of Conifers.^ — Dr. Wille gives particulars of the size 

 and distribution of the bordered pits in Conifers, especially in Pinus 

 sylvestris, P. Larix, and P. Abies. He finds that in each section (zone) 

 of the stem the outer and the inner border of the pits do not attain 

 their full size for about ten years, the size remaining after this nearly 

 constant. The border of the pits in the autumn-cells is nearly of the 

 same size in all the annual rings. No rule can be laid down with 

 regard to the relative size of the pits at different heights in the stem. 



Accumulation of Reserve-substances in Trees.§ — Dr. E. Hartig 

 has determined, as the result of a number of experiments, that the 

 purpose of the accumulation of reserve-materials in the trunks of trees 

 is to supply tlie material for the production of seeds ; and that the 

 periodicity in the occurrence of good fruit-years depends on the gradual 

 collection of food-supplies, which are then used up in the abundant pro- 

 duction of seeds. 



Fibrovascular Bundles in the Petiole of Nierenbergia rivularia.|| 

 — M. Lamounette states that the petiole of Nierenhergia rivularia is 

 slightly winged on the two sides. If a transverse section be made of an 



* Naturwiss. Wochenschr., iii. (1888) pp. 19-21 (1 pi.). See Bot. Oentralbl., 

 xxxvi. (1888) p. 266. 



t Bot. Gazette, xiii. (1888) pp. 3] 2-6. Cf. this Journal, ante, p. 84. 



t Ber. Naturf. Gesell. Halle, (1887) 1888, pp. 1-39. 



§ Bot. Ztg., xlvi. (1888) pp. 837-42. 



II Bull. Soc. d'Hist. Nat. Toulouse, xxiv, (1888) pp. xviii.~xxi. 



