RELATION BETWEKN GONIDIA AND HYPH-E IX LICHENS 171 



The problems presented at the commencement of the work had to 

 be divided as follows : 1 . What is the nature of the gonidia ? 

 2. How close is the relation between the hyphae and the gonidia, and 

 what is its character? 3. Is the point of view of Elfving in an}'' 

 way justified ? 4. Do the hyphce penetrate the algal cells, i. e. do 

 they form what is known as haustoria ? o. What is the further 

 development of the hyphal extensions after entering the gonidia, and 

 what is the effect upon the gonidia of their invasion by the haustoria ? 

 The following results obtained from these investigations more or less 

 answer the questions. 



In a thin section, made from the living thallus, certain areas can 

 be clearly distinguished in which chloroplasts are enclosed in an algal 

 cell wall. Side by side with the normal spherical cells with a well- 

 developed cup-shaped chloroplast can be seen pale gi'een cells obviously 

 differing from the normal. The character of these abnormal cells is 

 seen in the paleness of colour, the contracted and deformed chloro- 

 plast, and even in the entire absence of contents, so that one sees even 

 empty cellulose envelopes of these gonidia. I cannot consider this a 

 normal condition of the cells which will be described as "pale gonidia." 

 They have a protoplasmic structure from which chlorophyll is entirely 

 absent ; these gonidia, in an altered condition, are often found in 

 considerable numbers and present many successive changes from the 

 normal gi-een cell to the empt}' gonidial envelope. In this connection 

 A. A. Elenkin investigated abundant material, and observed that the 

 disorganisation of the gonidia increases in the deeper parts of the 

 thallus, where the zonal character is found to be the result of the dis- 

 tribution of the dead remains of gonidial cells. These gonidial 

 remains are scarcely noticed among the green gonidia and hypha?, but 

 it is only necessary for a reagent ClZnl to come into contact with 

 the cellular tissue, to bi-ing them distinctly into view in the fonn of 

 violet-coloured spherical envelopes and shapeless little masses whose 

 connection with the gonidia, without the use of a reagent, would be 

 absolutely impossible to imagine. It is interesting to note that in 

 the staining of the gonidia, different sections of the same thallus 

 appear very dissimilar. In many preparations a whole series of 

 changes in the gonidia could be observed, from deep staining to 

 perfect absence of it. As far as it was possible to judge, the gonidia 

 showing the greatest change from tlie normal were less deeply 

 stained. 



" Pale gonidia " at tii-st sight appear to differ from normal ones 

 onl}' in the absence of colour, but a more careful examination proves 

 beyond doubt that the difference goes considerably further. The 

 contents of the white gonidial cell stains practically the same as that 

 of the hyph* and are seen as small masses or even scattered about in 

 the form of a number of knots. " Pale gonidia " are also found in 

 which the contents have become separated into tiny spheres united 

 into a single mass. On the addition of ClZnl the " pale gonidia " 

 undergo the same changes as the normal green ones, the envelopes 

 becoming violet and the contents brown from the iodine, though 

 perhaps not to so marked an extent. When a watery solution of 

 methyl green is applied to a fresh section from the plant, the contents 

 ol the "pale gonidia," as also those of the hy])hal threads, takes a 



