ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 645 



Anatomy of the Osmundacese.* — D. T. Gwynne-Yaughan publishes 

 some remarks on the anatomy of the Osmundacea?. His summary is as 

 follows. 1. The early appearance of axillary pockets of xylem-sheath 

 parenchyma in the xylem of the sporeling stele of Osmunda is confirmed. 



2. The intrastelar origin of the pith in the Osinundacere is adhered to. 



3. The medullary rays are due to the breaking through of the xyleni- 

 ring by the xylem-sheath pockets, and are in consequence also intrastelar 

 in origin. 4. The mesarchy found in the basal region of the leaf-trace 

 in Thamnopteris and Zalesskya is still occasionally retained in the early 

 leaves of Osmunda regalis.^ 



Prothallia of Equisetum. f — (i. Perrin discusses the prothallia of 

 Equisetum. In the Polypodiaceas the prothallia are much more frequently 

 unisexual and apogamous than is generally indicated. In Equisetum, on 

 the other hand, unisexual prothallia are not so general as is commonly 

 supposed ; hermaphroditism is frequent enough. The author experi- 

 mented with E. silvaticum, E. arvense, E.palustre. The spores do not 

 necessarily lose their germinative faculty within ten days ; if kept in a 

 slightly moist atmosphere they are still good after a month. But in dry 

 air they perish quickly. This is due to the thinness of their cell-wall. 

 If they can be kept without unrolling their elaters they retain their 

 power of germination for over a fortnight, even in dry air. After 

 germination the prothallia are mostly unisexual ; when male they are 

 digitate, with the antheridia on the ends of their branches. When they 

 are female they are more compact and cordate cushion-like, with the 

 archegonia buried. Frequently these female prothallia show fully 

 developed antheridia on their periphery — rarely in E. arvense, frequently 

 in E. sylvaticum and E palustre. There is much in common between 

 the spores and prothallia of Equisetum and the Polypodiacese ; in both 

 when the prothalba are unisexual, they are very digitate ; and when 

 they are female, or hermaphrodite, they are cordiform. In both cases 

 adventive prothallia can be obtained. External factors have a strong 

 influence over the sex in the two categories. 



Life-history of Salvinia natans.J — K. Yasui gives an account of 

 the life-history of Salvinia nutans, with the following conclusions : 

 1. The primary tapetum-cells of both sporangia are formed by division 

 of the archesporial cell, and they again divide into one layer of many 

 cells. 2. The spore-mother-cells are eight in the macrosporangium and 

 sixteen in microsporangium. 3. The number of chromosomes of the 

 spore-mother-cell is sixteen and the reduced number in the spore is 

 eight. 4. During the reduction-division the tapetum-cells begin to 

 degenerate and nourish the spores. 5. Sixty-four mature spores are 

 formed in a microsporangium, but in a macrosporangium only one spore 

 becomes mature. 6. The male prothallium consists of a large pro- 

 thallium-cell, a small root-cell, two sterile cells, and two antheridia, 

 which consists of a wall-cell and a central cell. The central cell divides 

 twice, and in each of the four cells a spermatozoid is formed. 7. The 



* Ann. of Bot., xxv. (1911) pp. 525-36 (1 pi. and figs.). 



t Comptes Rendus Acad. Sci. Paris, cliii. (1911) pp. 197-99.. 



t Ann. of Bot., xxv. (1911) pp. 469-83 (3 pis,). 



