LIXDSAY, ON xVBROTHALLUS. 59 



dissociation, and dissolves out the colouring matter, rendering- 

 distinct the terminal cell and its septum. In some cases a 

 delicate colourless membrane appears to overlie and connect 

 the apices of the paraphyses, but is really probably a thin 

 layer of the mucilage or intercellular substance already 

 refeiTcd to. 



The spores are usually about ttV 5 ^^ t-jV (J inch long by -j^o o 

 to 4 oVo broad ; they are rather longerthan those of A. Smithii, 

 but about equal in breadth. They vary greatly both in size and 

 form. Normally, they are ellipsoid, with acute extremities ; 

 colourless or pale yellow, having a double contour, and 

 usually a lemon- coloured globular nucleus, arranged in the 

 central axis, at either end. But they are sometimes lanceolate, 

 fusiform, or caudate ; or they are short and broad, swelling 

 nearly into an ovoid or spheroid. In the latter case there is 

 sometimes only one nucleus ; or, if two, they are eccentric. 

 In some cases the spores are empty, or fidl apparently of a 

 homogeneous, colourless, oily fluid, resembling in this respect 

 many of the stylospores ; or they are filled with globules and 

 granules of different size. The latter condition occurs in an 

 abortive form or a permanently undeveloped type ; and also 

 in the old state, in which the nuclei become broken up into 

 globules and granules. In certain states, when devoid of 

 nuclei, the spores bear a resemblance to those of some Pel- 

 tigeras and Stictas. Like the spores of A. Smithii, they 

 appear to be arranged in the tliecae in a spiral manner. Their 

 nuclei are much more constant in their occurrence than those 

 of the spores in A. Smithii ; they occupy those portions of 

 the spore which, in the latter species, become the loculi. 

 They germinate like many other spores, sending out a deli- 

 cate filament from one extremity. They are, says Tidasne, 

 " nucleo inaequali heterogeneo ^ixque (saltem de specie) oleoso 

 gra^ddfe, in sinu eujuslibet asci inordinate generantur." I do 

 not fully comprehend this description. The intra-thecal 

 development of the spores I have already described when 

 referring to those of A. Smithii. 



The spermogones I have seen more or less abundantly in 

 specimens gro-wdng on P. saxatilis, fi^om Craigie Hill, Perth ; 

 Birnam Hill, Dunkeld; various parts of the Highland 

 road between Blairgowrie and Braemar; various localities 

 round Braemar ; Ben Nevis; Barmouth, Wales, and other 

 localities ; and also on Cetraria glauca and P. conspersa from 

 the latter locality. They occur as extremely minute, black, 

 point-like bodies on the surface of the thallus, scarcely dis- 

 cernible by the naked eye. With the aid of a good lens, 

 each of the point-like spots is found perforated in its centre 



VOL. V. G 



