i»8 
W. Watson. 
nella, Eurhynchium, Brachythecium, Plagiothecium, Amblystegium, 
and Hypnum are not confined to xerophytes, though their function 
may be of a similar nature. 
(b) Hyaline Cortical Cells of the Stem are found in some plants, 
which are apparently hydrophytic (e.g., Sphagna and Hypnum 
pellucidum) and have a similar function. 
(3). Mucilaginous Cells. 
Mucilaginous cells absorb a large quantity of water which can 
then be distributed to the plant according to its needs. They are 
not abundant except in a few plants, but are generally formed 
during gametangial development and fertilisation, and are often 
present as mucilaginous hairs at special places which require to be 
kept moist, such as the growing point (e.g., Pellia), gemmae-forming 
bodies (e.g., Blasia), etc. 
(a) Mucilage cells are present in the thalli of Conocephalum 
(Fegatella), Lunularia, Anthoceros, Grimaldia, etc. 
( b ) Symbiotic gelatinous Algce. Nostoc and other Cyanophyceae 
is present in special cavities in the Anthocerotales (3) and Blasia. 
(c) Associated Algce are often found in the axils of the leaves, 
or otherwise associated with them. They usually have gelatinous 
walls, and mostly belong to Myxophyceae (Cyanophyceae). Species of 
Nostoc are the most common but I have found many others— 
Glceocapsa , Tolypothrix , Oscillatoria, Scytonema, Chroococcus, Glceo- 
thece, Microcoleus , Symploca, Phormidium, Cylindrospermum, Ulothrix 
subtilis, Glceocystis, etc. 
(5). Hypogeal Tubers, Etc. 
Hypogeal swellings which not only serve as organs for the provision 
of reserve material, or for the formation of new plants, but also act 
as water-storers, e.g., the tubers of Anthoceros, Gcothallus (3), 
Fossombronia tubifera (7) and Petalophyllum. The hypogeous 
“ rhizomes ” of Stephaniella, according to Goebel (7) “ are the 
morphological equivalents of the flagella which are found in many 
Hepatics, and they are able to grow out into leafy branches.” 
(6). Succulent Tissue. 
This method of storing water, though common amongst the 
spermophytes is of infrequent occurrence in the bryophytes, and is 
never very pronounced. 
(a) Succulent leaves. CEdipodium, a rare moss inhabiting earthy 
crevices of high mountain rocks, and the alpine hepatic Gymuomi- 
trium crassifolium, of bare moist soil, have somewhat thick leaves, 
