SPERMATOPHYTES— GYMNOSPERMS 329 



The immense sperms of the cycads, more than 100 ix in diameter, 

 can be seen with the naked eye. If the tip of the nucellus with the pol- 

 len chamber be removed when the sperms are mature, the large pollen 

 tubes, 300 to 500 /x in diameter, are very conspicuous. Even with the 

 naked eye, the movements of the sperm can be seen; and with a pock- 

 et lens one can see some details. Place the piece of nucellus on a slide 

 in a drop of water, but without any water on the pollen tubes, and 

 examine with a 16 mm. objective. The amoeboid movements of the 

 sperm, and also a quick movement reminding one of the sudden jerky 

 movement of Vorticella, are easily seen; and, by closing the dia- 

 phragm a little, some movement of the cilia should be distinguishable. 

 Zamia is the only genus available in the United States; but even its 

 rather small female cones, as they near the fertilization stage, will keep 

 4 or 5 weeks after they have been removed from the plant. 



In the region of Miami, Florida, pollination takes place late in 

 December or early in January; blepharoplasts appear in March, and 

 swimming sperms are found during the first 2 weeks of June. In north- 

 ern Florida, all stages are 2 or 3 weeks later. If one is so fortunate as 

 to get cones of Ceratozamia, the sperms should be found from the last 

 week in June through the second week in July. 



Oogenesis. — The ovules of the Cycads and Ginkgo are very large, 

 and, when mature, thin sections cannot be cut by any method yet 

 discovered. In younger stages it is not difficult to get good sections of 

 the entire ovule. Slabs should be cut from two sides of the ovule to 

 facilitate fixing and infiltration. During free nuclear stages in the 

 endosperm, and even during earlier stages in the formation of walls, 

 care must be taken that the slabs may not cut into the endosperm, or 

 even too near to it, for the endosperm is so turgid that it may even 

 break out or, at least, will be distorted. Even after the ovule ap- 

 proaches its full size, it can be cut entire, until the stony layer begins 

 to harden. Paraffin sections of the entire ovule, cut 15-20 /x thick, and 

 stained rather lightly in safranin, gentian violet, orange, make very 

 instructive preparations. When the fresh ovule can no longer be cut 

 easily with a razor, it is not worth while to try to cut it in paraffin. 

 Interesting preparations may be made by cutting from the median 

 longitudinal portion of the ovule a slab about 5 mm. thick. The slab 

 should be fixed, washed, dehydrated, and cleared in xylol. It should 

 then be kept in a flat-sided bottle. Such a preparation shows the 

 integument, micropyle, nucellus with its beak, pollen tubes, the stony 



