240 HICKS, ON GOMDIA OF LICHENS. 



some valuable observations,* has sprung up — that many 

 organisms of the class alluded to are but a condition of the 

 growth of the gonidia of lichens. 



To add new facts to those already published, tending in 

 the same direction, will be the endeavour of the following 

 contributions, and which, it is confidently hoped, will tlu-ow 

 additional light on this confessedly difficult subject. 



And it may be well at the commencement to remark that 

 the gonidia of lichens have extraordinary powers of dissemi- 

 nation, far beyond what is generally recognised. From a series 

 of observations, extending now over many years, in which they 

 were never absent, I found that they may be collected in 

 comparatively great numbers from snow and rain, par- 

 ticularly the former, and especially in windy weather. The 

 quantity of gonidia, frequently with attached fragments of 

 lichens, entangled and brought down by the snow, generally 

 considerably exceeds that of any other organic molecules. 



Experiments upon this point maybe easily made by placing 

 a clean sheet of glass in the open air during a fall of snow. 

 When a sufficient quantity has fallen, it should be melted, 

 and the snow-water allowed to run into a tube ; the super- 

 natant fluid being poured off after the foreign matter has 

 subsided, I have noticed sometimes that the discoloration of 

 the water is in a great measure dependent on the gonidia of 

 lichens. These I have kept in the water for some months, 

 and have seen them passing through the same varieties of 

 segmentation to be described below as occurring in the 

 gonidia of lichens and in " Chlorococcus" Hence it will be 

 seen that every surface upon which snow or rain can fall 

 must have a number of these gonidia deposited upon it during 

 the year. In the course of the following communication it 

 will be seen that these organisms have the property of in- 

 creasing to an unlimited extent by subdivision, and thus will 

 be explained how enormous surfaces are covered by the so- 

 called " Chlorococcus." 



Now, although the gonidia of the various lichens are 

 wafted by air-currents hither and thither, doubtless to very 

 distant points of the globe, yet we may for the same reason 

 expect the unicellular algse and their allies, if really derived 

 from them, would, in any given district, vary according to 

 the species of lichens prevalent in that district ; and this 

 I have found, so far as my observations have extended, to 

 be the ease ; for although the gonidia of many lichens are 

 scarcely to be distinguished from each other, yet there are, 



* See 'Bo!aiiLso!ie Zeitung,' 5th January, L855, I. II. Ibid., 1S55, 

 Herm. ll/.igbolm. '.Microscop. Diet.,' art. " Palmellaoese." 



