100 ON THE PLANT-CELL. 



critical selection of the facts, but afterwards goes to work as uncritically 

 as possible. Two circumstances conduce to render the earlier observa- 

 tions of Ingenhousz, Agardh, Wrangel, Wilke, Girod- Chantrans, and 

 others, entirely useless, or, at all events, very suspicious; in the first 

 place, because the above-named observers were not sufficiently assured of 

 the identity of the motionless and moving corpuscles, and secondly 

 because, owing to the then state of science, and the nature of their instru- 

 ments, they were not at all in a condition to distinguish between true 

 Infusoria and the minute spores of the Confervce, &c. To which, also, 

 may be added that, as regards the Confervcz, many things have been 

 looked upon as spores which were merely cell-contents, as starch, chloro- 

 phyll-granules, &c., and which consequently, very naturally, occasionally 

 exhibited the molecular motion. 



As a proof of the good grounds I have for this scepticism, I would 

 merely remark, that an observer like Kiitzing, who has devoted thirteen 

 years, with the most unwearied industry, to the observation of the Algce, 

 ventures to state in his whole work but three instances in which he him- 

 self had an opportunity of observing the phenomenon in question. 



As facts of a more certain and useful nature, only a few observations 

 remain, in which it was noticed that the spore-cells were liberated and 

 exhibited spontaneous motion, but afterwards became motionless and 

 germinated. The latter circumstance especially must necessarily be 

 inquired into in referring to the older observations, because we also know 

 as a fact that true Infusoria are actually met with in the interior of the 

 cells of Confervce. Acting in an earnest spirit of criticism, which 

 alone will suffice to secure us from being misled by the dreams of 

 fancy, I can admit but very few of the facts adduced by Meyen 

 in his " Physiologic " and Annual Reports, all of which have re- 

 ference to spore-cells, partly of the Conferva and partly in the fila- 

 mentous Fungi. To these, also, are to be added some later observations 

 by linger *, Kiitzing f, and Thuret J . I have succeeded in observing a 

 phenomenon of the kind in question in two plants only, viz., in Achlya 

 prolifera and Vaucheria clavata DeC. This observation is quite suffi- 

 cient, however, to place the fact itself beyond doubt. Achlya prolifera 

 presents two kinds of spores : larger ones, which are formed in smaller 

 number in spherical sporangia ; and smaller ones, which are developed in 

 greater numbers in the unchanged filiform terminal joints, from which, 

 when the spores are mature, a minute operculum is detached. Shortly 

 before this, the spores assume a vibrating motion, which is accompanied 

 with change of place, often considerable. This motion lasts for some time 

 after the spores have escaped, and finally ceases, whereupon the spores 

 frequently, even after a few hours, begin to germinate. When a terminal 

 joint of this kind is emptied, a new similar joint usually grows within it, 

 arising from the next septum, and frequently not wholly filling the 

 remaining former one. In this new joint, also, spores are again formed, 

 which have then, in making their escape, to pass two openings, and 

 occasionally move about for a long time between the two cell- walls before 

 they reach the second opening. But it also happens, that they never 

 arrive at this second opening at all, and germinate, or at least begin to 

 germinate, within the older utricle. 



* Unger, Die Pflanze ittt Momente der Thierwerdung, 



f Kiitzing, Phycologia generalis. 



I Thuret, Les Organes Locomoteurs. 



