Tliom — Fertilization in Aspidium and Adiantum. 293 



the tip of the cytoplasmic end of the sperraatozoid. 

 The nature of the body is still questionable. It has been 

 shown by Belajeff for the Equisetaceae to be the origin of the 

 cilia. Webber, Ikeno and Shaw find the same to be true. 

 This function points toward a relationship with the centro- 

 some in lower plants as described by Strasburger or in ani- 

 mals as has many times been shown. But beyond serving as 

 the origin or point of attachment of the cilia it develops no 

 function. It does not act as a centrosome in nuclear division 

 (see Ikeno's own figures), and is lost before fertilization, so 

 fails to perform the two chief functions of a centrosome. 

 Guignard, investigating the spermatogenesis of Chara, found 

 the earliest change was the formation of a darkly staining line 

 just inside (possibly outside) the nucleus which develops into 

 the head end of the spermatozoid and contains little or no 

 chromatin. His description, although he regarded the body 

 as inside the nucleus, corresponds to a large extent with the 

 recent observations of the development of the blepharoplast. 

 In my own material no such change appears at first. I have 

 not been able to determine exactly when the cytoplasmic for- 

 ward or head end is formed, but certainly the earliest change 

 involves only the nucleus. 



Our chief interest, however, lies in the transformations which 

 occur in the nucleus. In figure 27 we see the notable 

 changes taking place. The nuclei have become elliptical and 

 in some cases pointed at one end. The chromatin appears in 

 the form of granules deeply stained (blue) on a network of 

 achromatic material or linin. This network is massed near 

 the surface of the nucleus. The prominent nucleoli (stained 

 red) occupy a more central position. Two of them appear 

 in each cell, but in figure 28 part of the cells contain 

 three instead of two, so that although the position of the 

 nucleoli with reference to each other indicates multi- 

 plication by division, the number present is not essen- 

 tial. The nucleus now lying very near one side of 

 the cell becomes flattened tangentially into a band lying just 

 under the wall with its concave depression toward the center 

 of the cell. In this concavity we find the blepharoplast 

 (figs. 29, 36). The flattening process is accompanied by the 



