358 The Ohio Naturalist. [Vol. XV, No. 1, 



In rti}'' studies, therefore, careful observations of the spirem 

 were made with the view of detennining whether there is a con- 

 tinuous thread or whether there are a number of short individual 

 threads interwoven but distinct as described by Lawson and others 

 in a number of cytological studies of plants more or less closely 

 related to S. herbacea. 



The exact manner of chromosome formation was also studied 

 to determine whether they were the result of a looping and a 

 later longitudinal folding, or if there was simply a transverse 

 constricting and breaking apart of the spirem to form the chromo- 

 somes as described by Miss Elkins in Smilax herbacea. 



It was with these points in view that this study and review 

 of the necessary literature was taken up under the guidance of 

 Prof. John H. vSchaffner, whose assistance and advice was found 

 to be of inestimable help in all work undertaken with him. 



GENERAL CONSIDERATION OF PAST LITERATURE ON THE SUBJECT. 



Since in recent years all except the latest papers have been 

 repeatedly reviewed, it is not considered necessary to refer to any 

 except such as have a very direct bearing on the matter in hand. 

 Those dealing with plants closely related to Smilax herbacea are 

 however included so far as they are available for study. 



Miss Elkins in her paper, "The Maturation Phases in Smilax 

 herbacea, " states that she did not find a distinct reticulum in the 

 microsporocytes, and often the chromatin bodies were in pairs 

 or fours scattered through the finely granular meshes. According 

 to her account the multinucleolate condition is the rule rather 

 than the exception and often the nucleoli have papillate pro- 

 jections which are present quite late. At "synapsis" or contrac- 

 tion there is nevermore than one nucleolus present which condition 

 is brought about by the union of the nucleolar elements, but often 

 there are dark staining bodies left in the nuclear cavity. She 

 also found that the nucleolus disappears at the metaphase just 

 as Gates found for Oenothera rubrinervis. In the presynaptic 

 stages, the linin ineshes are said to contract, drawing the chro- 

 matin material together, while the nucleolus is at one side pro- 

 jecting from a mass of threads. It is during this period that 

 she found the chromatin becoming arranged into an interwoven 

 beaded filament. The appearance of the nucleus after synizesis 

 is stated to be quite different from its previous condition, the 

 chromatin emerging as a homogeneous fiJanient. It is also 

 vaguely suggested that this may facilitate proper placing of 

 the paired parental elements in the chromosomes in the spirem. 

 She says that the chromosomes do not appear as definitely united 

 until the segmentation of the spirem. After synizesis the spirem 

 is a fairly thick thread, slightly beaded, but in a short time becomes 

 homogeneous. She observed that the double character of the 



