190 PROCEEDINGS OF THE ACADEMY OF [1893. 



At the apex of the gland proper, a cap is noticeable, fig. II, A, Z> 

 which was more highly refractive than the remainder of the cell wall. 

 Directly below it the protoplasm seemed more dense, the proto- 

 plasm itself was yellow or brownish, granular and in part showed 

 reticulations. Since I did not examine fresh material, I cannot, at 

 present, say how far the protoplasm had been affected or altered 

 in appearance by the alcohol. 



The outer envelope or portion which I have for want of a better 

 term called " sheath," is delicately walled, sometimes closed at the 

 top, fig. II, A, and sometimes open, fig. II, B, C, D. The wall 

 is transparent — almost colorless. This sheath, in all probability, 

 represents the " epithelial cells " of Gray, but instead of being epi- 

 thelial cells rapidly formed and ruptured, the observation of the 

 method of development of these sheaths indicates a totally different 

 explanation regarding their true nature. The method of secretion 

 witnessed in glandular hairs is generally as follows : " The secre- 

 tion regularly occurs first at the apex and spreads from there, lifting 

 off the thin cuticle in shape of a bladder whose contents are then 

 filled with the secretion." 1 Regarding fig. VI, where a sheath is 

 just beginning to be formed, S", and where another has already 

 attained a considerable size, S', there can be little doubt of the 

 fact that the method of secretion in case of the glandular hairs of 

 Brasenia peltata is entirely in accordance with that observed in 

 glandular hairs generally. The sheath then is nothing more nor 

 less than the cuticle lifted off by the secretion. The cuticle, as will 

 be seen on comparison of the figures, is capable of growing or 

 becoming stretched to a remarkable extent ; this may be especially 

 well seen in fig. VT and fig. VIII, both glands being taken from 

 near the vegetative point where secretion seemed most active. The 

 cuticle finally becomes broken, indistinct, and eventually seems to 

 dissolve, as indicated in fig. II, C & D. A peculiar rupture of the 

 cuticle witnessed in a few cases is shown in Fig. II, B. This was 

 perhaps caused by some external agency, since, usually, the sheath 

 seems to become indistinct rather gradually instead of a portion 

 breaking off with a smooth edge. 



According to Hanstein, the cuticle of glandular hairs in case of 

 unopened leaf-buds after rupture is often regenerated, and the form- 

 ation of new secretion begins. 2 This process is particularly evident 



'Julius Sachs, Vorlesungen liber Pflanzen Physiologie, Leipzig, 1887, p. 195. 

 2 DeBary, Vergleichende Anatomie, Leipzig, 1877, p. 104. 



