﻿1 903 J NUCLEAR MEMBRANE 3 1 3 



carefully followed in the pollen mother cells of Passiflora, and is 

 here taken as the type, many other forms were also studied. 

 Among these were the pollen mother cells of Cobaea, Gladiolus, 

 Hedera, Lilium, Smilacina, and the archesporial cells of Equise- 

 tum. In all of these forms the process of nuclear membrane- 

 formation was found to be practically the same as that described 

 for Passiflora. In certain cases, however, it was found that in 

 the accumulation of the karyolymph and the dividing of the 

 chromatin mass the process differs slightly. This was particu- 

 larly evident in the archesporial cells of Equisctimi limosnm. 

 Here, as in Passiflora, the chromosomes unite to form a single 

 mass of chromatin at each pole of the spindle [Jig. p). In the 

 next stage, however, instead of only two or three lacunae 

 appearing in the chromatin, a large number make their appear- 

 ance [fig. 10), These increase in number, grow indepetidently, 

 and do not flow together in this early stage as they do in Passi- 

 flora. The result is— as shown in figs, 10, 11, 12 — that in sec- 

 tion view we do not have that ring-like appearance of the chro- 

 matin which was found to be so characteristic of Passiflora. 



Fig. II shows a condition in which the lacunae have increased 

 to such an extent as to extend beyond the chromatin, and the 

 contained karyolymph is therefore directly exposed to the cyto- 

 plasm in these places. The result here, as shown in fig. n, is 

 an incomplete membrane surrounding each daughter nucleus, 

 with the membrane only visible in those regions where the 

 cytoplasm is exposed to the karyolymph. 



From the above observations it would seem that as the 

 chromatin of the daughter nucleus divides up in its preparation 

 to pass into the spirem condition there is secreted a watery 

 fluid commonly recognized as the karyolymph or nuclear sap. 

 The karyolymph is first contained within the chromatin mass, 

 but its volume increases and extends be^'ond the chromatin and 

 consequently comes in contact with the cytoplasm. There 

 seems little question that it is the exposure to the cytoplasm 

 which causes the formation of a membrane around the nucleus, 

 and the nuclear membrane is therefore a cytoplasmic struct- 

 ure. 



