276 REV. J. M. CROMBIE ON THE ALGO-LICHEN HYPOTHESIS. 



simple or branched, are constantly directed straight forwards, 

 without any twisting about to hunt for algals, even were any such 

 present. And yet at a slightly more advanced stage of growth, 

 you would, on microscopical examination, detect plenty of gonidia 

 in these specimens. "Whence, then, and how, do these originate ? 

 If the hyphae are not parasitical on the gonidia, may it not be 

 that the gonidia are parasitical on the hyphae ? — an alternative 

 at one time suggested, but which evidently is as untenable as 

 Schwendenerism. The matter, however, lies in a nutshell, and 

 admits of a very easy explanation. On a further inspection of 

 the specimens, you will readily perceive upon the surface of the 

 hypothalline stratum the presence of a number of small, variously 

 coloured glomerules, with which it is more or less sprinkled. 

 These are formed at an early stage of the evolution of the hypo- 

 thallus, at or towards its centre, and in immediate proximity 

 to where the spore first germinated*. On auatomical dissection 

 it is found that these glomerules consist of minute cellulose 

 granules, in the cellules of which are to be seen the gonidia in 

 various stages of evolution. From the fact of their thus occur- 

 ring in a growing condition, and the impossibility of their enter- 

 ing from without through the closed walls of the cellules, it is 

 evident that the gonidia originate in the glomerules themselves 

 (just as the spores do in the apothecia), and are consequently self- 

 developed organs of the lichen. Now these glomeruli constitute 

 the first parenchymatous tissue which is directly developed upon 

 the hypothallus. Like all the other elements of the thallus, this 

 parenchyma is formed, as Nylander has well expressed it (vide 

 * Flora,' 1879, p. 3 J3), " by an innate power or impulse of procrea- 

 tion which is inherent in the spore itself, and is not communicated 

 from any foreign source, the only assistance rendered being, as 

 already noticed, the materials derived from the atmosphere, espe- 

 cially in the form of rain-water." 



The glomerules, of which (as may be seen from the specimens) 

 one or more are put forth at the same time, gradually become 

 more numerous and contiguous, as the process of development 

 goes on, until at length a continuous cortical stratum is formed 

 upon the hypothallus. It certainly seems very strange that 

 these cortical cellules in which the gonidia arise should be either 



* Specimens illustrating the earlier stages of lichen-growth (which of course 

 never appear in herbaria) seem to be entirely unknown to the supporters of 

 Schwendenerism . 



