2 W. P. Wilson. 



Iris Pseudacorus, Salix and Vitis vinifera ^] are a few of the many illus- 

 tralioDS wliich raight be given of plants exhibiting this phenomenon. 



Also some of the Fungi, such as Pilobolus crystallinus and Mucor mu- 

 cedo give fine examples of the excretion of small drops on the surface of 

 plants. Other instances of the excretion of water are presented in the 

 pitchers of Sarracenia and Nepenthes, on the leaves of Pinguicula, Drosera 

 and Dionaea. Still further is to be mentioned the excretion of water on 

 the so called nectaries, which are of so universal occurrence in the flowers, 

 and often on the leaves of plants. 



Up to the present tirae, with but one exception^) this excretion of 

 water, i. e. the bleeding of plants, the appearance of water on the various 

 parts of leaves, and the occurrence of the more or less sweet fluids on the 

 surface of nectaries has been ascribed to one and the same cause, pressure 

 from wilhin the plant. Either the so called root-pressure, or the pressure 

 exerted in the stem or leaf-parts, from cells or groups of cells more or less 

 near the point of excretion have been made to explain Ihese various phe- 

 nomena 3) , 



I propose in the present investigalion to deal with the phenomenon 

 of excretion which takes place on the so called nectaries. 



These nectaries may be found on the petioles (Acacia lophantha), stip- 

 ules (Vicia faba), or blades (Prunus laurocerasus) of leaves. In the flower, 

 they may be on, or form a part of any of the organs, or they may be spe- 

 cial growths for themselves. In Fritillaria they form concavities on the 

 inner side and at the base of each of the six perianthal divisions. In Viola 

 they are a part of two of the five stamens. In many of the Liliaceae (Or- 

 nithogalum and Agapanthus) they form a part of the pistil. Often entire 

 Organs are changed into nectaries, as in Helleborus and Eranthis, where 

 the petals become cup-shapped nectaries. In many cases discs, or swel- 

 lings (Umbelliferae, Compositae) serve this purpose. Morphologically con- 

 sidered there is no unity whatever in the parts which may be appropriated 

 to this Office of excretion. 



We find at first in the study of the anatomy of the nectaries little 

 more in common than in the Morphology. Some nectaries are covered 

 with a thick cuticula while others are entirely devoid of the same; some 

 are provided with stomata through which the excretion finds its way to the 

 surface, while the great majority are without them. The epidermis cells are 

 sometimes disposed in one, oftener in two layers. A comparison of many 

 nectaries however determines several characteristics to be nearly universal. 



1) Moll 1. c. 



2) Pfeffer, Osmotische Untersuchungen 1877. p. 232. 



3) Sachs, Lehrbuch der Botanik 1874. p. 659. 



