ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 605 



forms : that of the canal, and that of the reservoir ; in the one case as 

 in the other, it is generally surrounded by a protecting sheath. The 

 two forms may be met with either isolated or united, but one never finds 

 reservoirs in roots, although they are often abundant in the leaves. 



Secreting Canals of XTmbelliferse and Araliaceae contained in the 

 Phloem.* — It is well known that to each vascular bundle in the leaf- 

 stalk of UmbellifersB there is in general a corresponding coUenchymatous 

 bundle beneath the epidermis, below vrhich runs a secreting canal, this 

 canal sometimes originating from a common source in the cambium with 

 the coUenchymatous bundle. In addition to these canals, Herr C. Miiller 

 finds, in the phloem portion of each bundle, canals, varying in number 

 according to its strength, which cannot in any case belong to the peri- 

 cycle. These were observed especially in Astrantia and the allied 

 genus Hacquetia. They are always closely associated with those in the 

 collenchyma. Their size and the number of secreting cells surrounding 

 each canal vary with the species. Their origin does not appear to be 

 always the same. The cavity of the secreting cells is usually much 

 larger than that of the adjacent phloem-cells, and the outline of their 

 cell- wall much sharper. 



Herr Miiller gives a list of a large number of species of Umbellifera9 

 in which these phloem-canals were observed ; the highest number observed 

 in a single phloem was eleven. The number of secreting cells belonging 

 to each canal varied between two and nine. In a smaller number of 

 species of UmbellifersB the most careful observation failed to detect the 

 presence of phloem-canals. 



In the Araliacese phloem-canals were found in the leaf-stalk of a 

 number of species ; but they were usually less numerous than in the 

 Umbelliferte, mostly only one canal in each phloem. 



Influence of the Turgidity of the Epidermal Cells on the Stomata.f 

 — According to Herr E. P. C. Schafer, the opening and closing of the 

 pore of the stoma is due to the relative intensity in the action of two 

 opposing forces, — the turgidity of the guard-cells, and the smaller 

 turgidity of the adjoining cells of the epidermis. The stomatic appa- 

 ratus exercises an independent function of its own; and the author 

 contests the theory that the guard-cells are compressed by an external 

 force originating in the turgidity of the adjacent epidermal cells. In the 

 stomata of Azolla the opening and closing of the pores takes place in the 

 ordinary way, although the guard-cells are destitute of the thickening- 

 bands which are elsewhere characteristic of them. 



Anomalous Cells in the Interior of the Tissue of Fossil Plants. J — 

 Prof. W. C Williamson describes the occurrence of " intrusive " cells 

 lodged in the interior of " host-cells " in the remains of plants from the 

 coal-measures. They occur in parenchymatous tissue, in the interior of 

 scalariform vessels or tracheides, and within macrospores belonging to 

 the Lycopodiacege. In the case where they occur within vessels they 

 appear to be genuine examples of thylosis; those found in paren- 



* Ber. Deutsch. Bot. Gesell., vi. (1888) pp. 20-32 (1 pi.). 



t Schafer, R. P. C, 'Ueb. d. Einfluss des Turgors d. Epidermiszellen auf d. 

 Function d. Spaltoffnungsapparates,' 45 pp., Berlin, 1887. See Bot. Ceutralbl., 

 xxxiv. (1888) p. 49. 



X Ann. of Bot., i. (1888) pp. 315-23 (1 pL). 



