SUSPECTED PARASITISM IN A MOSS. 207 



of blue-green algae. The algae commonly found in these situations, 

 are colonies of Nostoc embedded in soft mucilage, colonies of another 

 blue-green with tough mucilage and filaments of Scytonema. Under 

 the microscope, these appear as masses of algal cells or filaments. 

 The rhizoids of the young plants enter into the algal masses and come 

 into intimate contact with them. In a few more days, the young 

 plants produce a great number of gemmae from the axils of the 

 leaves near the tip of the stem. These get detached and are distri- 

 buted beyond the area of the' wall originally covered by mosses, 

 and get mixed up with the algae growing in these regions. In 

 the outskirts of the older patches, the rhizoids of the young plants 

 grow into the new substratum and give rise to protonema filaments 

 which are covered by masses of blue green algae. Gradually new moss 

 plants appear in these regions and the spreading of the moss on the 

 wall continues. It is a matter of constant observation that no new 

 plants develop in regions of the wall where the algae have not already 

 appeared. 



Protonemal Stage. — A microscopic examination of the out- 

 skirts of the moss patches, where to all outward appearance no moss 

 plants but only algae are found, show masses of protenema filaments 

 or germinating gemmae. The protenema filaments arise from rhizoids 

 of young plants further up or from hibernating rhizoids of the 

 previous season which had extended so far. The protonemal filaments 

 branch frequently and are mixed up with algal masses and soil 

 particles. 



In the preparation of slides, the lime substratum was dis- 

 solved with dilute HCl and the sand particles left behind were 

 removed by careful teasing with fine pointed needles. The material 

 for mounting, both in the case of protonema and also in the case of 

 rhizoids of the moss plants in different stages, was prepared in this 

 way, stained and mounted in glycerine. 



The greater part of the protonema branches were bright green in 

 colour with prominent chloroplasts. But the tips of the filaments in 

 many cases and some of the branches gradually became colourless and 

 finely branched. (Fig. 2.) This colourless portion was always in inti- 

 mate contact with the algal masses. During teasing, it was often 

 noticed that the green portion was easily detached from the algal masses 

 but they always had their ends broken. Light crushing of the al°al 

 mass and differential staining showed that the colourless tips of the 

 protonemal filaments extended into the gelatinous masses of algae and 

 there spread in between the algal cells. In some, where the algae form 

 soft gelatinous masses, the branches had short beaded cells which 

 occupied the centre of the mass. In others, where the algae had tough 



1766—27 



