330 SUMMARY OF CURRENT RESEARCHES RELATING TO 



Synedra Ulna, is a special case, and unlike other such movements is not 

 shared by all the chromatophores at the same time, but successively 

 according to age. The tendency of the daughter-chromatophores to 

 separate as far as possible from one another is probably connected with 

 their need to obtain the requisite amount of light and nourishment. 



Chromosomes in Osmunda.* — S. Yamanouchi has studied the 

 chromosomes in Osmunda cinnamomea during both homotypic and 

 heterotypic mitoses, and finds that the reticulum of the young nucleus 

 consists mainly of chromatin material, and arises from the chromosomes 

 of the previous division. There is no indication of pairing of knots or 

 strands in the chromatin network during the resting stage. Although it 

 is difficult to trace the limits of the chromosomes during the resting stage, 

 they appear to retain their individuality. Pairing of chromatin material 

 occurs only during the prophase of heterotypic mitosis. The pairs are 

 in closest association during synapsis, but no actual fusion occurs. No 

 splitting takes place during heterotypic mitosis, but the bivalent chromo- 

 somes result from the association of two independent chromosomes. 

 Separation of each pair gives an appearance of longitudinal splitting. 



Structure and Development. 



Vegetative. 



Physiological "Separating-Layers"in Gymnosperms, Equisetaceae, 

 and the Bryophytes.t— M. Plant publishes the results of extensive 

 observations made upon Gymnosperms, Equisetum and Bryophytes as to 

 the presence and significance of the endodermal layer. The Gymno- 

 sperms examined include members of the Cycadaceae, Coniferae, Gink- 

 goaceae, and Gnetaceae. The Cycadaceae have a specially characteristic 

 endodermal layer. All the Cycads and most of the Taxaceaa, Cupressineae, 

 and Taxodere have an "intercufcis" in their roots, but this is absent in 

 all the Gnetacea? and usually in the Abietineas. The development of 

 the endodermis is alike in all Gymnosperms, and there is always a 

 primary and a secondary endodermis. In the hypocotyl the endodermis 

 varies much in all Gymnosperms, but a primary endodermal layer is 

 usually present. The aerial axis has neither endodermis nor starch- 

 layer, and this is also true of the leaves. The latter possess semi- 

 cutinised cells, the function of which is still unknown. Some new and 

 interesting facts concerning Equisetum have been brought to light. The 

 cuticle of the epidermis of the aerial stem is normal, but that of the 

 rhizome is variable. Lignin is only present in the vascular bundles and 

 in the spiral thickenings of the sporophylls. This latter fact appears to 

 be of phylogenetic importance in connection with this group. Suberised 

 and cutinised cell-lamellae are not present, neither is there any " intercutis " 

 or cork-formation. A primary endodermis is always present. The 

 Bryophytes cannot be shown to possess any endodermal layer. 



Saxifragacese.J — E. Warming has studied the arctic species of 

 Saxifragaceae with the following results. There are five types of stem- 

 structure, viz., the Primula type with a vertical, sympodial rhizome and 



* Bot. Gaz., xlix. (1910) pp. 1-12 (1 pi.). 



t Jahrb. wiss. Bot., xlvii. (Leipzig, 1910) pp. 121-85 (3 pis. and 1 fig.), 

 j Structure and Biology of Flowering Plants, i. (1909) pp. 168-236 (40 figs.). 

 (Reprint from Meddel. om Gronland, xxxvi.) 



