202 REPRODUCTION 



spermatia and, generally, with a mass of mucilage that swells with moisture 

 and secures their expulsion. 



The spermatia of lichens are colourless and are provided with a cell-wall 

 and a nucleus. The presence of a nucleus was demonstrated by Moller 1 in 

 the spermatia of Calicium parietinum, Opegraptia atra, Collema microphyllum, 

 C.pulposum and C. Hildenbrandii, and by Istvanffi 2 in those of Buellia puncti- 

 formis (B. myriocarpa\ Opegrapha subsiderella, Collema Hildenbrandii, Cali- 

 cium trachelinum,Pertusaria communis andArthom'a communis (A. astroidea). 

 Istvanffi made use of fresh material, fixing the spermatia with osmic acid, 

 and in all of these very minute bodies he demonstrated the presence of a 

 nucleus which stained readily with haematoxylin and which he has figured 

 in the spermatia of Buellia punctiformis as an extremely small dot-like 

 structure in the centre of the cell. On germination, as in the cell-multi- 

 plication of other plants, the nucleus leads the way. Germination is preceded 

 by nuclear division, and each new hyphal cell of the growing mycelium 

 receives a nucleus. 



c. GERMINATION OF SPERM ATiA(pycnidiospores). The strongest argu- 

 ment in favour of regarding the spermatia of lichens as male cells had always 

 been the impossibility of inducing their germination. That difficulty had at 

 length been overcome by Moller 1 who cultivated them in artificial solutions, 

 and by that means obtained germination in nine different lichen species. 

 He therefore rejected the commonly employed terms spermatia and spermo- 

 gonia and substituted pycnoconidium and pycnidia. Pycnidiospore has 

 been however preferred as more in accordance with modern fungal termi- 

 nology. His first experiment was with the "spermatia" of Buellia punctiformis 

 (B. myriocarpa} which measure about S-IO/A in length and about 3 M in 

 width, and are borne directly on the septate spermatiophores (arthrosterig- 

 mata). In a culture drop, the spore had swelled to about double its size by 

 the second or third day, and germination had taken place at both ends, the 

 membrane of the spore being continuous with that of the germinating tube. 

 In a short time cross septa were formed in the hyphae which at first were 

 very close to each other. While apical growth advanced these first formed 

 cells increased in width to twice the original size and, in consequence, became 

 slightly constricted at the septa. In fourteen days a circular patch of my- 

 celium had been formed about 280/4 in diameter. The development exactly 

 resembled that obtained from the ascospores of the same species grown in the 

 absence of gonidia. The largest thallus obtained in either case was about 

 2 mm. in diameter after three months' growth. The older hyphae had a 

 tendency to become brownish in colour; those at the periphery remained 

 colourless. In Opegrapha subsiderella the development, though equally 



1 Moller 1887. * Istvanffi 1895. 



