684 
Frit sc h and Haines .— The Moisture-relations 
communicated in the present paper are the outcome of an attempt to 
study the mechanism involved. The problem was first approached by 
an investigation of the effect of various strengths of plasmolysing solu¬ 
tions. For this purpose Tidman’s sea-salt was selected, so as to avoid 
possible inaccuracies due to the toxic action of single salts on the proto¬ 
plasm. 
The material investigated was primarily the same as that employed in 
the first paper (Fritsch, 1922 , p. 2), but relatively little of the Hormidium- 
stage of Prasiola crispa was obtainable during the course of the work, and 
it has consequently not been dealt with as fully as some of the other forms. 
Apart from these, investigations were also made on (a) a form of Hormi- 
dium jlaccidum occurring in some quantity in different parts of the Redlands 
woods in Surrey; ( b) Cystococcus humicola , Naeg., growing on wooden 
palings in Dorking; and (c) moss protonema (probably belonging to the 
moss Hypnum cupressiforme , L., var. filiforme , Brid.) from the Redlands 
woods. A practice was made of collecting the material for the different 
successive experiments from as small an area (often only a few square 
feet), as possible, so as to ensure relative uniformity (cf. p. 697), but this was 
not always feasible, and for some of the forms there were two or more 
collecting grounds. 1 There is, however, no reason to suppose that these 
habitats differed at all essentially from one another. Most of the ex¬ 
perimental work was carried out at East London College, but some at 
North Holmwood, Surrey. The bulk of the observations were made during 
the winters of 1922 and 1923 and the early spring of 1922, since suitable 
material was not easily obtainable during the dry summer weather. 
In the course of our investigations numerous problems have been 
approached, a detailed solution of which lay outside the scope of the 
present paper (cf. especially section E). We propose to deal with some 
of these in later communications. 
A. The General Behaviour towards Plasmolysing 
Solutions. 
It is noticeable that, if material of these terrestrial forms is placed in 
plasmolysing media, some of them require solutions of very considerable 
1 1 he following is a list of these habitats and of the experiments in which the respective 
materials were used: ( a ) For Zygogonium ericetorum: (i) little-shaded pathway (Expts. I, III); 
(ii) unshaded pathway (Expts. IV, V, IX, X, XII, XVI, XX); (iii) somewhat shaded pathway 
(Expts. XXXI, XXXV, XXXVI). (b) For Hormidium Jlaccidum : (i) on sandy vertical bank at 
side of pathway (Expt. II) ; (ii) bare clayey soil, in great part shaded by a.large holly (Expts. VI, 
XI, XXXII, XXXVI) ; (iii) sandy path, fully exposed to the light (Expts. XIV, XXVI, XXIX). 
(0 Moss protonema (all from same habitat as (ii) for Hormidium). (cf) For Pleurococcus : 
(0 wooden palings on outskirts of Dorking (Expt. VII) ; (ii) wooden palings, South Holmwood 
(Expts. XVII, XXIV, XXVIII, XXX, XXXVI). 
