482 SUMMARY OF CUERENT RESEARCHES RELATING TO 



formation, without reference to the part of the thallus to which they 

 belonged. 



Of purely vegetative organs with limited growth, the wall of 

 the cupule was the only one examined, and in this the new formations 

 always originated at the base. The same was also the case with 

 Marchantia polymorpha. The receptacle and its pedicel exhibited the 

 same phenomena. If the latter is separated from the thallus, whether 

 with or without the receptacle attached to it, vegetative shoots arise 

 from its base, but at different heights, according to the vital con- 

 ditions. When female receptacles are detached, the adventitious 

 shoots spring either from near the cut surfaces or from the furrows 

 on the under side of the rays of the receptacle. Separate rays, or even 

 their outer ends, gave birth to such shoots from their base. 



With regard to the cause of the phenomenon, the author agrees on 

 the whole with Pfliiger's view. He believes that the locality and the 

 nature of the newly formed organs do not depend on the accumulation 

 of specific nutrient substances, but on the structure of the proto- 

 plasmic framework and the mode of combination of its molecules. 

 They are connected also with the properties of the gemmee or 

 bulbils. 



Experiments on the development of the gemmje in Marchantia 

 and Lunularia showed that the direction of the first division-wall, 

 and the consequent eventual form of the organ, do not depend on 

 gravitation ; every separate portion of the bulbil exhibits a polarity 

 which the author again refers to the arrangement of the molecules in 

 the protoplasmic framework. 



Attention was paid also to the histological structure of the 

 adventitious shoots from the thallus, the pedicel of the receptacle, 

 and the receptacle itself. In sections of the thallus these shoots 

 always spring from the undermost cells of the cortex, or, when this 

 is wanting, from the undermost layer of the parenchymatous tissue ; 

 the ventral cortical layer of the mid-rib displays especial capacity 

 for cell-division. When the shoot is being formed, the growing 

 point appears behind its centre, and only subsequently occupies its 

 normal lateral position as the result of displacement. Several shoots 

 are usually formed side by side in the ventral furrow of the pedicel 

 and in the furrows which pass along the rays of the receptacle. In 

 both cases they originate by division of the outermost cortical cells 

 which line the furrows. 



Abnormal Development of the Sporogoniuin of Lejeunia.* — Dr. 

 K. M. Gottsche describes a peculiarity in the structure of the 

 sporogonium in many species of Lejeunia from widely separated 

 localities, consisting in the excessive development of the parts de- 

 signed for the protection of the fructification. The entire envelope 

 appears to be composed of two superposed parts; the upper part 

 retains its normal structure adapted to assist the development of the 

 capsule and the spores, while the lower portion exhibits an unusual 



• SB. Gcsell. Bot. Hamburg, Feb. 26, 1885. See Bot. Centralbl., xxv. 

 (1886) p. 255. 



