i8o 
Notes . 
Treub J , in his elaborate paper on the apical meristem of the roots 
of monocotyledonous plants, tried to make out the apical meristem of 
the main roots themselves. According to him these have distinct 
initials for the plerome, common initials two layers thick for the peri- 
blem, dermatogen, and the calyptra, but at the same time he found 
that in the calyptra further divisions take place by means of which it 
acquires a certain amount of independence. He ascribed this structure 
also to Iridaceae, Sparganium , Buiomus, and doubtfully to Alisma. 
The next who took up the same subject was Flahault 2 . He ex- 
amined the adventitious roots 3 of Eichhornia eras sipes and the primary 
roots of Pontederia cordata , L. The primary roots of P. cordata have, 
according to him, distinct initials for the plerome, two or three com- 
mon initials (on longitudinal section) for the periblem and dermatogen, 
and distinct initials for the calyptra. In studying the structure of the 
apical meristem of the adventitious roots of Eichhornia crassipes, he 
came to the conclusion that the characters of the apex of these roots 
are not absolutely fixed, and that the initials of the different tissues 
may become more or less specialised. But he shows that he is not 
quite certain about this point by adding that the epidermis may very 
likely be independent of the cortex even at the apex of the root, though 
he never observed this fact in the embryo of Pontederia cordata , and he 
concludes by saying that the epidermis, when once differentiated, does 
not take any part in the formation of the rootcap. 
Flahault says that he hesitated a long time before he came to the 
above-mentioned conclusions. Perhaps he would not have done so if 
he had not used the same method in preparing his sections as Treub 
— boiling in a solution of calcium chloride till nearly all the water was 
evaporated. I think that this method is too severe for tissues so deli- 
cate as the apices of roots of water-plants. Much better results may 
be obtained by soaking the sections in potash for twenty-four hours, 
treating them with acetic acid and then mounting in glycerine. Some- 
times I have examined sections in glycerine directly after they were cut, 
in other cases I stained them with Kleinenberg’s haematoxylin after 
treatment with potash, and mounted them in Canada balsam. I found, 
like Flahault, that the characters of the apex of the adventitious roots 
1 Le radristeme primitif de la racine dans les monocotyledones, Leiden, 1876. 
2 Ann. des sciences nat. ser. 6, vol. vi. pp. 1-168 (Pontederiaceae, p. 50). 
3 Though he does not state distinctly that he used the adventitious roots for this 
investigation, this must be concluded from his remarks. 
