66 OrrR—LEAF GLANpS oF DIoSCOREA MACROURA. 
In this particular, the glands of Dioscorea macroura resemble 
the ‘‘ proteid-containing glands’’ of Ardisia, first described by 
Hohnel.* ‘These glands are likewise the home of a micro- 
organism, whose relationship to the plant, particularly in the 
case of Ardisia crispa, has been subjected to a critical investi- 
gation by Miehe.+ Other analogies exist, as exemplified by 
the parallel features of the glands in certain Rubiaceae, 
described by Zimmerman} and Boas. ‘This aspect of the 
glands will be discussed at a later stage. 
Standard tests for the detection of tannins were applied to 
thick sections of the acumen, but no trace of any such astringents 
could be found within the glands, which is in accordance with 
the findings of Correns, who failed to discover any tannins in 
the extra-nuptial nectaries. On the other hand, certain large 
elements of the ground tissue gave characteristic tannin 
reactions with iron salts, potassium bichromate, ammonium 
molybdate, cupric acetate and osmic acid. With Schultze’s 
solution, the whole of the glandular tissue was coloured dark- 
yellow, and the cuticularisation of the epithelial cell-walls became 
apparent, but neither with this reagent, nor with iodine and 
sulphuric acid, could a definite cellulose reaction be obtained 
in the thin cell walls of the secretory trichomes. No trace of 
oil could be found in any part of the acumen. 
The pronounced proteid character of the gland content, as 
disclosed by these microchemical tests, was further emphasised 
by a comparison of the nitrogen content of the acumen with that 
of the lamina. This was ascertained by the Kjeldahl method 
of analysis, applied to leaves taken from the living plant at 
intervals during the day. In every case, the tissue of the 
acumen was found to contain a much higher percentage of 
nitrogen than the tissues of the lamina. ‘The following table, 
in which the results of two of these nitrogen estimations are 
compared, will serve to illustrate this point. 
Nitrogen Content in 100 grams of Leaf Tissue. 
Time. amina. Acumen. Excess of N, 
| Content in Acumen. 
10.50 a.m. 246 mgs. 560 mgs. 314 mgs. 
4.30 p.m. 173 mgs. 486 mgs. 313 mgs. 
The remarkable difference between the nitrogen content of the 
acumen and that of the lamina, as shown by this process, could 
only be accounted for by the existence within the former, and 
Ya “Mice in Ber in Sitz. Ber. Wiener Akad., lxxxiv., abt. 1 ( 1882), pp. 
tA Zimmerman a 
PP- 574, 58 3° 
I. xxix. i 156 and hrb. fiir wiss 
nin jeer Sn a oe p. 29. )P. ? wae tain 
XXXVI. (1 903), p- 
