the Secretory Tissites of the Marattiaceae. 411 
Material and Methods. 
Material of the following genera and species was examined : 
Angiopteris evecta, Hoffm. Kaulfussia aesculifolia , Bl. 
Archangiopteris Henryi , Chr. et Gies, Marattia alata, Sw. 
Danaea alata , Sm. Marattia attenuata, Lab. 
Danaea nodosa , Sm. Marattia Cooperi , Mre. 
Danaea simplicifolia , Rudge. Marattia fraxinea, Sm. 
In order to eliminate at least one possible source of error, part of this 
material was carefully fixed in chromo-acetic or in acetic alcohol (glacial 
acetic acid, 1 part: absolute alcohol, 3 parts). The remainder was fixed in 
70 per cent, alcohol. 
For this investigation serial sections were necessary, therefore micro- 
tomed sections were cut (6/x- 1% ju), but care was taken to check the work 
by examining thick hand-sections. 
Various stains and reagents were employed, including safranin, gentian- 
violet, eosin, methylene blue, iodine, ferric chloride, Congo red, and haema- 
toxylin. 1 These were used singly and in combination. 
1. Development and Structure of the Mucilage-canals . 2 
Method i. Protogenetic Lysigenous 3 Mucilage-canals. 
The mucilage-canals of the Marattiaceae usually arise on the first 
differentiation of tissues at the growing-point of the stem or root. In the 
leaf also the very early differentiation of the canal-initials was observed. 
Both transverse and longitudinal sections through the young tissues of 
the stem, root, or leaf of by far the largest number of genera and species 
examined reveal scattered groups of cells, the canal-initials, which remain 
meristematic after the neighbouring cells of the ground-tissue have passed 
over into the permanent condition. These specialized cells usually divide 
into 2, 4, or 6 without any appreciable increase in size ; as a result of this 
cell-division groups of cells, which can readily be distinguished from 
the surrounding cells not only by their smaller size but also by their 
relatively larger nuclei and denser cytoplasm, are produced (Text-figs. 1-4 ; 
Plate XVIII, Figs. 6 and 12). 
1 This reagent was made up according to the formula published by Kleinenberg in Quart. 
Journ. Micr. Sci., Ixxiv, 1879, p. 208. 
2 In this paper the term £ mucilage ’ is applied to a substance (or substances) of unknown 
chemical composition, which exhibits certain recognized physical properties. For an account of 
the optical properties of various plant mucilages, including that of Angiopteris , see Schwendener, S., 
‘ Nochmals iiber die optisch-anomale Reaction des Traganth- und Kirschgummis,’ in Sitzungsb, 
d. Akad. d. Wiss. zu Berlin, Bd. ii, 1890, p. 1131. 
3 Frank, 1 . c. 
EC 2 
