ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 657 



were first seen in that stage of the first division of the mother-cells 

 when the nuclear membrane was still present, but twelve chromosomes 

 had already been differentiated. A strongly stainable centrosome lies 

 on each side of the nucleus, and on one of them the beautifully de- 

 veloped aster ( Stralilensonne) was seen as it partially forced itself to- 

 wards the interior of the nucleus ; while round the other one only a 

 number of minute granules could he detected. In the mother-aster 

 stage this was repeatedly seen, sometimes at only one, sometimes at 

 both ends of the nuclear spindle ; or two centrosomes were often visible 

 at the same end of the spindle, doubtless resulting from the division 

 of one. 



On the second division of the mother-pollen-cells, in addition to the 

 nucleus found in the knot, a centrosome was observed, sometimes of the 

 ordinary form, sometimes hour-glass shaped ; in the latter case probably 

 in the act of division. Both in the mother-aster and in the diaster 

 stage centrosomes are present at the two ends of the spindle. As soon 

 as four primordia of pollen-cells could be detected, the centrosomes 

 were no longer visible. In the place of one or two centrosomes, it was 

 not uncommon for the pole of the spindle to include a number of small 

 granules. 



Influence of External Conditions on the Streaming- of Protoplasm.* 

 — According to E. Josing, the influence of light on the streaming of 

 protoplasm is greatly affected by the external conditions. If objects 

 which display this streaming readily — leaves of Elodea, Vallisneria, or 

 Alisma, hairs of Tradescantia or Heracleum, internodes of Chara, <ke. — 

 are placed in pure water, the streaming is scarcely affected if they are 

 deprived of light. The case is very different if they are placed in 

 dilute ether. In the light, the streaming is then even more rapid than 

 in pure water ; but if deprived of light the movement is at once arrested, 

 to be again resumed when restored to the light. Light which has passed 

 through a solution of ammonium-copper- oxide acts in this respect the 

 same as darkness ; red light the same as white light. The removal of 

 carbon dioxide from the atmosphere produces the same effect as placing 

 in ether or chloroform. 



Cytology of Erythronium. f — J. H. Schaffner continues his study 

 of the life-history and cytology of Erythronium (albidum and america- 

 nvm), which he compares with that of Lilium.^ In the germinating 

 pollen-tube the pollen-tube nucleus takes a very light stain, and is com- 

 paratively small, while the generative nucleus is large, and is surrounded 

 by dense-staining protoplasm. In the archesporial cell the chromatin 

 network is very distinct ; after the formation of the spirem the nucleus 

 and the chromosomes grow to a large size. Some of the nuclei of 

 Erythronium are of enormous size ; those in the walls of the ovule are 

 usually from 15 to 20 \x, in diameter, and the large reduction-nucleus 

 often measures from 40 to 50 /jl. No figures were seen in the entire study 

 which could be interpreted as a synapsis stage ; and the author main- 

 tains that what is usually called synapsis is a mere artifact. The 



* Pringshxim's Jahrb. f. wiss. Bot., xxxvi. (1901) pp. 197-228. 



t Bot. Gazette, xxxi. (1901) pp. 369-87 (6 pis.). Cf. this Journal, 1900, p. 605. 



X Cf. this Journal, 1897, p. 552. 



