2476 Journal of Applied Microscopy 



related to each other only through a common ancestry whose sexual organs were 

 ccenogametes. The Ascomycetes may represent two evolutionary lines derived 

 from a primitive coenocytic type of sexual organ (coenogamete). c. j. c. 



Lawson, A. A. On the relationship of the The spore mother-cells of Passiflora 



nuclear membrane to the protoplast. Botan- ai'ruka and the archesporial cells of 



ical Gazette, 35 : -Jos-liQ, pi. i =;, lOO"?. t^ • . t • h 



J J J y'or J y J tLqiitsetum iimosiim were especially 



studied, but observations were also made upon Lilium,Cobaea, Gladiolus, Hedera, 

 Pinus, Pteris and others. For comparison, several members of the Cyanophyceae 

 and lower Chlorophyceae were investigated. The principal conclusions are as 

 follows : The typical nucleus of higher plants is a water cavity structurally sim- 

 ilar to a cell vacuole. Chromatin is the only permanent constituent of the 

 nucleus. The karyolymph, linin, nucleoli and membrane are renewed at each 

 mitosis. The nuclear membrane is formed by the cytoplasm coming into con- 

 tact with the karyolymph just as the tonoplast of an ordinary vacuole is formed 

 by the cytoplasm coming into contact with the cell sap. The nuclear membrane 

 is of cytoplasmic origin and should be regarded as the inner limiting membrane 

 of the cytoplasm rather than as a constituent of the nucleus. In the Cyano- 

 phyceae and Bacteria there are chromatin granules which represent the nucleus 

 although they are not surrounded by any membrane or karyolymph. In the 

 forms of chlorophyce;ii which were examined, the karyolymph and nuclear 

 membrane were uniformly present. 



Flemming's stronger solution, diluted one-half with water, was used for fixing 

 and the safranin, gentian-violet, orange combination for staining. Sections were 

 cut 1-3. 6/< in thickness. c. j. c. 



„,. ,. I. r TT u L In the previous papers of this series 



Wisseiingh, C. van. Untersuchungen uber ^ ^ ^ 



Spirogyra, Vierter Beitrag zur Kenntniss der the writer has devoted his attention tO 



Karyokinese. Bot. Zeit. 60: 1 15-138, pi. 5, ^he nucleolus and the nuclear network. 

 1902. 



The present contribution deals with the 



nuclear membrane, the spindle and the behavior of the walls of the vacuoles. 

 Spirogyra iriformis, a form with thin walls and loose, delicate chromatophores, 

 was chosen for study. Material was fixed in Flemming's solution, after which 

 it was treated with a strong chromic acid solution (40 per cent.) which dissolved 

 successively the cytoplasm, karyoplasm and nucleolus. The spindle, however, 

 was not dissolved. Sections do not seem to have been used. 



During the earlier stages of karyokinesis the nuclear membrane is entirely 

 resorbed. The spindle is derived from the granular cytoplasm about the nucleus 

 and consists of but one kind of fibers, the two different lengths of fibers and the 

 two opposite groups described by Strasburger for S. polytcpniata not appearing 

 in S. triformis. The spindle fibers do not grow through the nuclear membrane 

 as described by Strasburger. The spindle is at first multipolar, but becomes 

 bipolar. There is no diminution in the number of spindle fibers during karyo- 

 kinesis, but after karyokinesis the spindle becomes resolved into cytoplasm. 

 The spindle fibers resist the action of chloral hydrate and so are easily dis- 

 tinguished from cytoplasmic strands. The walls of the vacuoles are also made 

 visible by chloral hydrate. During karyokinesis the walls of the vacuoles with 



