Oogonium Lil»eration and th9 Embryogeuy of Some Fucaceous Algae. 7 



I often came across some detached branches of Ciist. Tumeric 

 floating on the sea near the Marine Biological Station ; and the 

 receptacle on the branches bore many discharged oogonia within 

 the mass of entangled paraphyses. Thus the rapid growth of 

 paraphyses at the time of the oogonium liberation appears to be a 

 characteristic of the genus CystopliiiUum. 



II. Early Stages of Embryogeny. 



Since the appearance of Oltmanns' classical work on 

 Fucaceae'\ it has been generally beheved that in tiie Fucaceae in 

 general the three successive nuclear divisions in the oogonium 

 take place before the formation of oosphères, no matter how many 

 oosphères come to function in one oogonium. 



At this stage of the discussion Miss E. B. Simons' paper on 

 Sargasswn filipemlula-^ attracted the attetion of plant morphologists. 

 According to her, in this alga the three successive nuclear divisions 

 before the oosphère formation are entirely suppressed and the one 

 nucleus of the oogonium initial remains in a resting condition 

 throughout the entire period of growth of the oogonium and 

 becomes directly the nucleus of the single oosphère, 



During my stay at Misaki, I paid special attention to this 

 point and was so fortunate as to be able to observe the successive 

 developmental stages of the oosphère in the oogonium of Sargas- 

 swn and Cystophyllmn. The result of my observations differs, 

 however, remarkabley from that of Miss Simons; namely the 

 oogonium development in these algae is quite normal, showing 

 the usual three successive nuclear divisions in the oogonium. 



As a matter of course, the periodical oogonium liberation is 

 accompanied by the periodical development of the oogonium. 

 All the oogonia in one conceptacle are liberated at one time, so 

 the developmental stage of all the oogonia in one conceptacle is 

 always the same. In other words, differing from the other cases 



1) Oltmanns, Beiträge zur Kenntnis der Fucaceen. Bibl. Bot. Cassel, 1898. 



2) Simons, A morphological study of Sargasmm ßlipendnla. Bot. Gaz. XVIX. 1906. 



