6.2 LINDSAY, ON ABROTHALLUS. 



Ijably an illusory appearance due to adhesion of some of the 

 abundant floating, free spermatia. These filaments generally 

 terminate in a rounded bulging extremity, the interior of 

 which contains a more or less finelj^ granular material. 

 From their abundance, growing as they do from among the 

 sterigmata, they are apt to conceal the latter. They occur 

 also in the spermogones of several other lichens — such as 

 Parmelia physodes, and some of the Ramalinea and Umbili- 

 caria. The nature and function of these peculiar filaments 

 have not hitherto been determined. Possibly they are 

 abortive and hypertrophied sterigmata ; or their terminal 

 cells are tlirown ofl:' as accessory reproductive bodies of a 

 kind with which we are as yet unacquainted. Fiu'ther re- 

 searches of course are necessary to settle this point. 



In specimens of A. oxysporus, growing on P. conspersa, the 

 spermogones of theAbrothallus and Parmelia are apttobe con- 

 founded. One of the most prominent characters of P. conspersa 

 is its black-punctate thallus ; hence, indeed, its very appro- 

 priate name. The minute black points, so aljundantly 

 scattered over its sui'face, are the spermogones. These 

 thalline spots are each perforated by an ostiole which leads 

 into the cavity of an immersed, spherical, one-locular sper- 

 mogone. Here^ however, as in the analogous case of P. 

 saxatilis, the resemblance ceases ; for the sterigmata and 

 spermatia are much more delicate or slender, and the former 

 are articulated, each joint being a narrow linear cell. Its 

 spermogones are frequently also dotted over the outer surface 

 of the thalline exciple of the apothecia, and also on the 

 hypotheeium, after the falling out or erosion of the hy- 

 menium or lamina proligera. The falling out of the latter 

 leaves a saucer- or eup-shaped organ of similar colour to the 

 thallus. 



In searching for spermatia, it is necessaiy to bear in mind 

 that the spermogones precede, in order of development, the 

 apothecia; and that, by the time the latter have attained 

 matm'ity, the former have been long since emptied of their 

 contents. Young spermogones containing spermatia should, 

 therefore, be looked for on young or sterile thalli or lobes, or 

 on those bearing only nascent apothecia. I have found the 

 spermogones in best condition on portions of thallus destitute 

 of apothecia. The same remark may be applied to the 

 pycnidcs of A. Smithii. Though strong grounds exist for 

 regarding the spermatia as fertilizing or impregnating cor- 

 puscles, the process of impregnation has not been hitherto 

 detected in lichens. It still remains a problem for micro- 

 scopists. The discovery of spermogones in lichens has already 



