304 



BOTANY. 



reviewing the subject, affirms that the actual development of 

 a gonidium from the end cell of a hypha has not been ob- 

 served. Nylander even goes so far as to declare that in no 

 case do the filaments themselves give birth to gonidia, but 

 that they "have their origin in the parenchymatous cortical 

 cells which are observed on the prothallian filaments of ger- 

 mination."* 



401. The recent observations of Dr. Minks,f if con- 

 firmed, will put to rest the question as to the origin of go- 

 nidia. He studied the small green cells sometimes called mi- 

 crogonidia, and makes the announcement that they originate 

 in the interior of the cells of every portion of the lichen- 

 thallus, viz., the cortical and medullary cells, the paraphy- 



ses and young asci, and 

 even the spores and 

 spermatia. The proto- 

 plasm in the cells forms 

 an axial column, which 

 becomes broken up into 

 rounded bodies of a pale 

 greenish color ; these 

 finally become covered 

 by cell-walls and after- 

 ward escape from the 

 mother-cell as free mi- 

 crogonidia. He asserts 

 that intermediate forms of all degrees are to be met with be- 

 tween microgonidia and gonidia. Dr. Muller,in making simi- 

 lar observations, arrived at the same conclusion J as to the 

 origin of the microgonidia. 



The third view as to the origin of gonidia is so intimately 

 connected with the question of the real nature of the gonid- 

 ium and its functional relation to the hypha?, that it can 

 only be explained by taking these into consideration. 



* In Flora, 1877, p. 256, as quoted in Revue Mycofagique, p. 4, 1879, 

 and in "Grevillea," 1879, p. 91. 



f For accounts of these observations see Flora, 1878, Revue Mycolo- 

 yique, 1879, and American Journal of Science and Arts, 1879, p. 254. 



J Flora, 1878. 



Fig. 211. Soredia of Usnea barbafa. A, sore- 

 dium, consisting of one gonidium covered with 

 hyphae ; B. of many gmiidia formed by division ; 

 C, the gonidia pepuratt- d by hyphte ; I) and E, the 

 soredia developing into new lichen plants. X 

 500.- After Schwendcner. 



