130 BOTANICAL GAZETTE [avcust 
oa s N in 15° of filtrate 
_ Tissue Percentage of N W — fissue from tannic acid 
. precipitate 
Leaves of mature plants........ 0.68 2.9418m 0.02048" 
sepeweroyamne Pods... 26... sae: 0.39 5.130" 0.0240 “ 
Developing seeds.............. 0.95 2.105 0.0283 “ 
From such results as these it is impossible to tell how much of the 
nitrogen found in the filtrates from the tannic acid precipitation is 
due to products of the digestion of Witte peptone and how much is 
non-proteid nitrogen present in the tissues used. Moreover, Witte 
peptone is not completely precipitable by tannic acid, certain of the 
very soluble peptones not being thrown. down by that reagent. In 
remaining estimations of comparative ereptic power two dige> 
tions were made with each tissue, one a boiled control. As before, 
the quantity of tissue taken was that which should contain 0.02% of 
nitrogen. The digestion mixtures were made up to 308” instead 
of 25%", as this quantity was found to be more convenient. Mois 
ture determinations were also made on each tissue so that compat 
sons of the dry weights could be made. The results of this study at 
given in the accompanying table. 
The table shows that although the method is not absolutely exact 
yet fairly good duplicates are obtained in different digestions with 
€ same tissue. The digestion in a number of cases was Vigorous 
noticeably so with the roots where more than half of the Witte pe? 
tone in the digestion mixture was hydrolyzed. - It should be said that 
= roots bore a few small tubercles which were removed so far 
possible, yet the minute ones remaining may have had some influ- 
ence on the results. It is suggestive to note that it is not the 
and cotyledons which contain the most enzyme per unit of nitrog™ 
ia Tather it is those tissues where active metabolism is occutTing: 
IS unfortunate that we are unable to use the weight of protoplast 
as a basis for comparison. The use of the nitrogen content : 
standard is well] enough between the various active tissues, but whes 
these are compared with tissues gorged with storage proteids 1 is 
evident that the Storage tissue contains far less protoplasm a 
ss weight of nitrogen. The error which the presence of sto 
Proteids introduces into our comparative results is evident in the cet 
