1 82 CALIFORNTA ACADEMY OF SCIEh'CES. [Proc. 3D Ser. 



EXPLANATION OF PLATE XXXIIL 



Figures drawn with Abbe's camera lucida. Zeiss, Apochromatic 

 Immersion Obj. 12 mm. 1.30 Ap. Compensating Ocular No. 6. 



Fig. I. A young pollen-mother-celL The cytoplasm is a clear network 

 which stains a light or gray-blue. The meshes of the network 

 appear to be smaller and radially elongated towards the 

 nucleus. There are numerous spherical bodies scattered 

 through the cytoplasm. They are stained black, probably by 

 the fixing fluid. The nucleus is quite large and shows a large 

 nucleolus and small oval chromosomes which lie immediately 

 upon the nuclear wall. The linin, which stains deep blue, is 

 of a lumpy or granular nature. 



Fig. 2. This figure shows the commencement of a remarkable differentia- 

 tion which takes place in the cytoplasm which immediately 

 surrounds the nucleus. A zone of granular substance, the 

 perikarj^oplasm, forms around the nucleus, which diiTers decid- 

 edly both in structure and staining qualities from the sur- 

 rounding network. While the outer cytoplasmic reticulum 

 stains a light or gray-blue, the granular substance stains orange. 



Fig. 3. This figure shows a later stage with an increase in the quantity of 

 perikaryopiasm about the nucleus, otherwise it does not differ 

 essentially from fig. 2. 



Fig. 4. Shows a still greater increase in the quantity of perikaryopiasm 

 about the nucleus. The black bodies are now beginning to 

 form a ring at the outer margin of the granular zone. 



Fig. 5. The perikaryopiasm has now reached its maximum and stands out 

 in the greatest contrast from the outer cytoplasm. The meshes 

 of the outer reticulum which abut on the perikaryopiasm are 

 small and apparently compressed, giving the impression of a 

 loose membrane which separates the two zones from one 

 another. It is impossible to trace any of the outer meshes into 

 the granular zone. They appear to have no connection with 

 the nuclear wall . The black bodies have now taken up their 

 position at the outer margin of the perikaryopiasm and form a 

 complete ring about it. 



Fig. 6. It will be noticed that in the preceding figures the linin is more or 

 less of the nature of a granular thread. It now appears to have 

 lost its granular structure and appears in the form of very fine 

 threads. We now have the first indication of the breaking 

 down of the nuclear wall, and at that part where the nuclear 

 wall is broken, the perikaryopiasm is commencing to take on 

 the form of a network and stains violet. 



