658 Beer. — Studies in Spore Development . III. 
of the reticulum into the spireme takes place. This spireme is seen to be 
longitudinally divided, and segmented into a number of separate pieces. 
9. A period of great nucleolar activity and of partial contraction of the 
spireme elements (‘second contraction ') then occurs. During this period 
the nucleoli are seen to be actively extruding droplets (or 4 buds ’) of 
material which pass into the nuclear cavity, where they adhere to the 
spireme filaments. A portion of this nucleolar material appears to be 
absorbed by the spireme segments and to contribute to their growth 
and staining power. 
10. The spireme segments, which are often bent into the form of loops, 
become gradually shorter, thicker, and more chromatic, until they can 
be recognized as unmistakable heterotype chromosomes. The whole 
process of the transformation of the spireme segments into the heterotype 
chromosomes can be followed so continuously that there can be but little 
doubt regarding the relation of one structure to the other. 
Each spireme segment consists of two univalent chromosomes arranged 
end to end, and each such pair develops, by concentration, into one of the 
bivalent chromosomes of the heterotype division. 
1 [. The number of chromosomes is about 115. 
1 2 . By vacuolation and the development of anastomotic connexions the 
material of the chromosomes becomes dispersed through the nuclear cavity 
during the telophase and a 4 resting ’ nucleus results during interkinesis. 
13. The spindle of the homotype division shows some variation in the 
mode of its origin. In some cases it is multipolar polyarch during the 
earlier stages of its development, in others it is multipolar diarch. 
Eventually it always becomes a bipolar structure. 
T4. The daughter chromosomes which reach the poles of the homotype 
spindle develop numerous branches and cross connexions, along which their 
substance passes, but no distinct vacuolation of their bodies could be seen 
during the telophase of the division. 
Bibliography. 
1. Beer, Rudolf : The Development of the Spores of Equisetum. New Phytol., vol. viii, No. 7, 
1909, p. 261. 
2 . Digby, L. : The Cytology of Primula kewensis and of other related Primula Hybrids. Ann. 
Rot, vol. xxvi, April, 1912, p. 357. 
3. Hannig, E. : Ueber die Bedeutung der Periplasmodien. I. Die Bildung des Perispors bei 
Equisetum . Flora, Bd. cii (Bd. ii, neue Folge), Heft 3, 1911, p. 209. 
4. Hofmeister, W. : On the Germination, Development, and Fructification of the Higher 
Cryptogamia, &c. English translation published by the Ray Society, London, 1862, 
pp. 266-306. 
5 . Osterhout, W. J. V. : Ueber die Entstehung der karyokinetischen Spindel bei Equisetum. 
Jahrb. f. wiss. Bot., Bd. xxx, Heft 2, 1897, p. 159. 
