514 SUMMARY OF CURRENT RESEARCHES RELATING TO 



nectaries of both stem and leaf. The nectary is formed at an early 

 period from a single epidermal cell, and the sheath from one or from a 

 very few cells lying directly beneath the mother-cell of the nectary. 



Elastic Stamens of Compositse.* — Prof. T. Meehan describes the 

 mode in which, in a large number of species of Composite, the column 

 of stamens matures its growth before the pistil becoaies fully elongated ; 

 the pistil, nnable to push through the column, bears it upon its apex 

 until the downward pressure is so great that the pistil bursts through, 

 when the elastic filaments at once draw the anthers down to their proper 

 position on a level with the limb of the corolla. The phenomenon is 

 attributed by the author to elasticity rather than to irritability. 



Glands on the Stamens of Caryophyllacese.t — Prof. T. Meehan calls 

 attention to the existence of glands at the base of the stamens in the 

 chickweed and other species of Stellaria, and in Cerastium and Arenaria. 

 At times these glands exude an enormous quantity of a viscid, slightly 

 sweet fluid, which does not appear to have for its primary function the 

 attraction of insects, since the chickweed is self-fertilized, though bees 

 do occasionally visit these flowers for the sake either of the nectar or of 

 the pollen. 



Fruit of Nycta^nese.J — According to Herr A. Heimeid the con- 

 version into mucilage of the outer layers of the fruit in this order is, 

 with a few exceptions, characteristic only of the Mirabiliese. The 

 absorption of water takes place always in a layer lying immediately 

 beneath the epiderm, which covers the surface of the fruit, consisting of 

 palisade-cells, the epiderm then peeling off. The drops of mucilage 

 exuded in this way sometimes contain starch-grains. The form of the 

 epidermal cells varies in the different groups. The author found calcium 

 oxalate to be a widely distributed constituent in the outer and often 

 also in the lateral walls of the epiderm of the fruit in the Mirabilieae ; 

 the form and arrangement of the particles of this salt vary greatly. 



Anatomy of Leaves. § — After restating the observations of Aresehoug, 

 Jonsson, Haberlandt, and others, on this subject, Herr O. Loebel gives 

 an account of his own observations, chiefly relating to details of structure 

 in the case of particular genera and species. 



The increase of surface of the palisade-cells, brought about by 

 foldings of their cell-walls, the author finds to occur alike in Dicoty- 

 ledons, Monocotyledons, and Ferns. The walls of the palisarle-cells are 

 composed of pure cellulose, and are usually thin; when thicker, they 

 are abundantly provided with pores. In both Monocotyledons and 

 Dicotyledons their position is occasionally oblique to the surface. The 

 spongy parenchyme usually contains but little chloropjhyll ; occasionally 

 starch is found in it. The parenchymatous sheath surrounding the 

 vascular bundles usually consists of a single row of cells from one and a 

 half to two times as long as broad ; in some land and water plants it is 

 altogether wanting. In cylindrical leaves the xylem-i^ortion of the 

 vascular bundles is surrounded by the phloem-portion. 



* Bull. Torrev B.t. Club, xvi. (1889) pp. 68-9. 

 + Pioc. Acad. Nat. Sci. Philad., 1888, pp. 396-8. 



t SB. Akad. Wiss. Wien, xcvii. (1889) pp. 692-703 (1 pi.). Cf. this Journal 

 1888, p. 82. 



§ Jahrb. f. Wis.?. Bot. (Pring.-heim), xx. (1889) pp. 38-77 (2 pis.). 



