LI0HENE8. 307 



slaves not at all related to tbe liyplise ; inTlie other tbey are produced 

 by tlxem, and after a brief period of freedom are fastened upon, and 

 compelled to do service for tbe byphae wbicb produced tbem. 



It is impossible to decide between these two theories until furiher in- 

 vestigations shall determine tbe truth or falsity of Dr. Minks' state- 

 ment as to the origin of microgouidia. It must, liowever, be said, that 

 tbe view wbicb appears to he most in accord withjvphat we now know 

 of plants, is that taken by Scbwendener. 



(ft) 1. Cultures of licliens have been made by many observers, 

 especially by Bornet, Reess, and Treub. Tbe latter made an extended 

 series, from which the following details of methods are condensed, 

 ^ores may be secured for germinatiou by placing freshly gathered 

 lichens upon plates covered with well-moistened glass slips, and keep- 

 ing them under a bell-jar for from twelve to twenty-four hours, at the 

 end of wbicb time a number of spores svill be found on tbe slides. 



3. The spores may be left upon the slides and allowed lo remain in a 

 moist atmosphere, as in a bell-jar. Others may be placed upon very 

 thin pieces of the bark upon which tbe lichens naturally grow. Still 

 others may be maie to grow in tbe presence of a small quantity of tbe 

 ash of the same species of lichen. 



3. A too copious supply of moisture is unfavorable to the successful 

 germination of the spores. If tbe conditions are favorab'e germination 

 will begin in from two to eight days. In about a month after sow- 

 ing, the protoplasm of the spore becomes in great part used, up in the 

 formation and elongation of the germinating filaments. It always bap- 

 pens that the growth of tbe hypbae from the spores ceases soon alter the 

 exhaustion of the protoplasm, unless the hypbae come in contact with 

 algae of the proper kind, or with gonidia. 



4. An interesting culture may be made by repeating Bornet's exper- 

 iment, as follows: He placed on fragments of bark, previously boiled 

 to kill all other germs, and also on pieces of limestone freshly broken, 

 a layer of Protococeus viridis scraped off of a damp wall, and to this 

 added tbe spores of TheloseJiistes paiielinvs. In about a, fortnight the 

 hypbae were seen to be large and ramified ; wherever tbey came in 

 contact with cells of the Protococous they adhered either directly or by 

 means of lateral branches. Bornet made at the same time parallel cul- 

 tures, without, however, bringing the germinating spores into proximity 

 to Protococeus ; tbe growth was much less, and in no case did he get 

 any evidence that the hyphse themselves formed gonidia. 



5. Treub modified Bornet's culture by using, in some of his experi- 

 ments, the artificially isolated gonidia of one species of lichen — for ex- 

 ample, of some species of Ramalina — and the spores of a different one, as 

 Theloschistes parielinus. He also used glass slides for bis cultures, 

 whether with gonidia or free algae, taking the precaution, however, to 

 allow the drop of water in which the spores and gonidia were placed 



