494 SUMMARY OF CURRENT RESEARCHES RELATING TO 



tinguish Lithothamnion from Lithophyllum. These genera are as a rule 

 the distinguished by differences in thair reproductive organs, and their 

 identity lias been difficult to decide in the absence of fruit. The 

 author finds that the anatomy of each genus is marked by the 

 following characters : Lithophyllum consists of a compact tissue in- 

 tersected by thick bands which separate the concentric layers of the 

 cells of the hypothallns, and arc due to the thickening of the transverse 

 walls. This applies equally to the horizontal and to the upright forms. 

 Lithothamnion, on the contrary, consists of a lax tissue composed of 

 chains of cells like a series of necklaces. These points are- shown in 

 figures. The author intends to show later that other genera, and even 

 species, can be determined by anatomical characters. 



Cytology of Floridese.* — The organs of reproduction in the Floridere 

 have been the subject of discussion by many authors, but L. Kurssanow 

 has still new facts to add to our knowledge. He gives a review of the 

 results of previous investigations, and summarises the opposite opinions 

 held on one' and the same point. He then passes on to describe his 

 own work on Helminthora divaricata and Nemalion lubricurn, which 

 resulted in the following conclusions : — 1. At no stage of development 

 of the carpogonium of Nemalion and Helminthora is the trichogyue 

 provided with its own nucleus. The carpogonium has always a single 

 nucleus ; and the trichogyne must be regarded as merely an outgrowth 

 from the carpogonium, not as an entire cell. Thus one can trace a 

 gradually ascending scale of development from the lower to the higher 

 forms of Floridea?, the simpler ones having a strictly one-celled and 

 one-nucleated female organ, while the more highly developed (including 

 Polysiphonia), according to Yamanouchi, possess a two-nucleated carpo- 

 gonium. In the latter class the trichogyne has its own nucleus, even 

 though it is not cut off from the rest of the cell. 2. The spermatia of 

 Helminthora and Nemalion have one. nucleus, and in normal cases never 

 have more. 8. Nemalion possesses a well-developed pyrenoid in the 

 centre of the chromatophore. It has a very complicated structure, 

 being composed of the central body of the surrounding zone. The 

 pyrenoid is distinguished by a remarkable sensitiveness to external 

 influences, swelling up easily and finally dissolving, leaving merely a 

 vacuole in its place. 4. A similar pyrenoid exists in general in Helmin- 

 thocladia, and probably in Helminthora. The central bodies and the 

 surrounding zone are distinguishable, the latter being filled with a 

 quantity of strongly colourable bodies, wdiich are often rodlike and 

 arranged radially. Schmitz's figure representing the pyrenoid as a 

 homogeneous body is explained by the fact that his preparations were 

 over-coloured and the small bodies in the surrounding zone were no 

 longer to be distinguished, so that the w T hole structure appeared as a 

 homogeneous ball. 



Connection between Cell-nucleus and Pyrenoid.f — M. von Derschau 

 communicates a, note on the connection between the nucleus and the 

 pyrenoids of cells in Chlorophycese. Lidforss has written on this 



* Flora, xcix. (1909) pp. 311-36 (2 tables). 



t Uer. Deutsch. Bot. Gesell., xxvii. (1909) pp. 99-100. 



