1883.] Significance of Water Glands and Nectaries. 45 



As to the glands of Limoniastrum and Poly podium, they 

 should be clearly separated from water-glands. The gland of 

 Polypodium certainly resembles to some extent that of a Dicoty- 

 ledonous gland, but the important distinction is, that the gland acts 

 independently of root-pressure, and as in Limoniastrum, by virtue 

 of the activity of the epidermal cells. It resembles, rather, a gland 

 of Limoniastrum, which is situated immediately over the termi- 

 nation of a vascular bundle, and differs materially from a water- 

 gland in the tremendous development of the tracheide tissue, as 

 well as in its physiological properties. 



One cannot but be struck hj the enormous activity of the 

 cells of the epidermal tissue, both in plants and animals. In 

 both cases it is from the epidermal, or epithelial tissue, that 

 well-nigh the entire secretory organs of the individual are derived. 

 The tissue of the epithem, on the other hand, is developed not 

 from the epidermal but from the fundamental tissue, and as far 

 « as its excretory powers go, in such glands as those of Saxifraga, it 

 contrasts wonderfully with a similar structure in the animal, viz. the 

 kidney, which is developed not from the hypoblast, but from the 

 mesoblast, and the cells of whose urinary ducts have, apart from 

 blood-pressure, but little excretory powers. In the plant epithem 

 the cells go so far as to store up in their interior, large quantities 

 of salts of Calcium and Magnesium, derived from the surrounding 

 tissue, but they cannot of their own activity excrete and get rid 

 of these salts. They cannot, as far as they nre concerned, go so 

 far as the excretory cells of the kidney. However, as regards 

 the epidermal cells of the plant, attention must be drawn 

 a second time to their wonderful activity, not only as demon- 

 strated by root-hairs, but also, as I have shown, by the cells of 

 the glands of Limoniastrum and Polypodium, and by the ordinary 

 hairs on the leaves of Fuchsia and the like. 



Nectaries 1 . 



Under the term nectary, which was first employed by Lin- 

 naeus 2 , are at the present time classed together a number of organs 

 differing greatly from one another, both as regards their structure 

 and their morphological value, but which are usually taken toge- 

 ther in consequence of the fact that they secrete nectar. When 

 we consider the tremendous differences as to morphological dignity 

 which exist between these organs, we may well ask, as did Clos 3 , 

 whether it would not be well that the name nectary should perish 



1 The very complete papers of Martinet, Ann. de Sc. Nat. 5th ser. Vol. xiv. 

 1872, Bonnier, 6th series, Vol. vin. 1879; and Behrens, Flora, 1879, give a full 

 account of all the literature with regard to this subject, and should be consulted. 



2 Linnaeus, Syst. Naturae et Phil. Bot. No. 86. 



3 Clos, Ann. de Sc. Nat. 4th ser. Vol. n. p. 23. 



