l8o BOTANICAL GAZETTE [mabch 



mitoses 



asm 



mitoses in the oogonium 



chiefly in Fucus platycarpus, and in a supplementary way in F. 

 serratus, by Strasburger, and mainly in F. vesiculosus, and in a 

 supplementary way in Ascophyllum nodosum, by Farmer and Wil- 

 liams. The detailed accounts given by these authors are devoted 

 chiefly to the last one of the three mitoses, the first and second mitoses 

 being touched only slightly. The following is a description of the 

 first two divisions in the young oogonium in Fucus vesiculosus. 



oogonium 



reticulum which is scattered irregularly throughout the cavity. The 



seems 



(fig. 40). One or two very large nucleoli 



asm 



generally lie isolated in the center, 

 very delicate alveolar structure,, which is very frequently interrupted 

 here and there by plastids, physodes, and black-staining spherical 

 bodies of undetermined nature. Toward the periphery of the nucleus, 

 the cytoplasm assumes a mixed structure of fine granules and fibrils. 

 The nuclear membrane seems extremely delicate. No polarity is 

 manifested in this resting condition. 



In very early prophase, a ragged chromatin reticulum gradually 

 passes into a thread, at first branched and then becoming simple. 

 As was described for the first mitosis in the antheridium, the trans 

 formation of the ragged chromatin into a thread is more active at the 

 periphery of the cavity, so that after a while the chromatin threac 

 are observed running irregularly and more abundantly along the 

 periphery than in the center, thus leaving the center nearly free from 

 chromatin (figs. 4Ia , 410 ). When the partial distribution of the 

 chromatin thread proceeds farther, the most of the tangled mass of 

 threads is located at one side of the nuclear cav 

 42b) showing the beginning of a typical synapsis. 



Coordinate with these internuclear changes, kinoplasm develops 

 and accumulates close to the nuclear membrane at a spot where it 

 associates with the synaptic group of the threads within the nucleus. 

 -I he threads gradually shorten and thicken. The irregularly tangle 

 threads now become regularly arranged into' loops. These loops 



(fig- 





