ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 635 



B. CRYPTOGAMIA. 



Cryptogamia Vascularia. 



Apical Cell in the Adventitious Buds of Ferns.* — Eecenfc investi- 

 gations by Zimmermann do not confirm the results previously obtained 

 on this point by Heinricher.| According to the last named, the adven- 

 titious buds of Asplenium bulbiferum jDossess at first a distinctly 

 recognizable apical cell, which disajDpears after the separation of a 

 few segments, again performing its normal function after the forma- 

 tion of the first frond. Such a temporary disappearance of the apical 

 cell would be an almost unique phenomenon in vegetable develop- 

 ment. As the results of a large number of observations, Zimmermann 

 was unable at any time to discover an apex without an apical cell, to 

 be clearly made out with the requisite precautions. It was not in 

 most cases to be directly recognized by its preponderating size ; but 

 unmistakably betrayed its nature by the regular course of the cell- 

 walls in the apical region. Nor was he able to confirm Heinricher's 

 description and drawing of a dejiression of the apical cell. 



A distinct apical cell was also made out in the adventitious buds 

 of Asplenium Belangeri, flahellatum, and Dregeanum. The adventitious 

 buds of Geratopteris, which are also very favourable for observation, 

 are distinguished from those of Asplenium bulbiferum by having a 

 more pointed apes. The apical cell is also considerably larger ; but, 

 as in Asplenium, separates segments on three sides. 



The author was unable to decide the point whether these adven- 

 titious buds spring from a single epidermal cell or from several. 



Muscineae. 



Influence of Light on the Thallus of Marchantiess.i: — The gemmte 

 or bulbils of Marchantia and Lunularia are perfectly symmetrical, and 

 it depends altogether on external conditions from which side the root- 

 hairs spring. The thallus, on the contrary, is dorsiventral, the upper 

 and under sides difi'ering from one another anatomically, the former 

 producing stomata, the latter root-haii's and leaf-like structures. A.s 

 in the case of the gemma3, however, it is determined by external 

 circumstances which surface becomes the upper and which the under 

 side. According to the view of Pfeffer the development of root-hairs 

 on one side of the gemmte is determined by gravitation, and is alto- 

 gether independent of the influence of light, a view contested by 

 Zimmermann, who maintains that, in addition to gravitation, light 

 exercises a considerable influence on the development of root-hairs. 



The experiment on which Zimmermann relies to establish this 

 position is to place the gemmfe in transparent receptacles on water, 

 lighting some of them from above and some from below, the latter by 

 means of a mirror, with the necessary precautions. If Pfefter's state- 

 ment were correct, it is obvious that in all cases root-hairs would be 

 produced only on the under side. Zimmermann found, on the con- 



* Bot. Centralbl., vi. (1881) pp. 175-6. 



t See this Journal, ii. (1879) p. 597. 



X Verhaudl. Phys.-Med. Ges. Wiirzburg, xv. (1881) pp. 247-52. 



