3GU SUMMAltY (X"' CUKUENT RESEARCHES RELATING TO 



alliance with the Flagellata ; hut the author regards the organism not 

 as belonging to the Flagellata, but rather as a Thallophyte, probably a. 

 transitional form to the Phseocapsacese, the probable phylogenetic origin 

 of the Phaeophyceaa. 



Chambers and Pores in the Cell-wall of Diatoms. *— Herr Ch 

 Miiller records the result of further observations on these points in the 

 structure of diatoms in connection with centrifugal growth in thickness 

 and extraneous protoplasm. He emphasises Schutt's distinction between 

 pores and dots, understanding by the former an actual perforation, by the 

 latter simply a thin spot in the cell-wall ; small circular dots which 

 resemble pores he calls " poroids." Pores in this sense are by no means 

 universal in the valve of diatoms. When present, it is not always 

 certain that the pores serve for the passage of protoplasm. In Melosira 

 undulata the pore-canals serve for metastasis and for pedicel-formation . 

 In Pleurosigma metastasis takes place through the pores, while locomo- 

 tion is effected by the raphe. In Epithemia the function of the pores is 

 unknown, locomotion is effected through the raphe, metastasis through 

 the dots. In Isthmia the function of the pores is also unknown - r 

 metastasis takes plaae through the dots. 



Pores through which a mucilage is excreted from which the pedicel 

 is formed (Gallertporen), can be detected without much difficulty in 

 Diatoma, where they occur only at one of the poles, and in many species 

 ot Synedra ; with great difficulty in Tubellaria ; in Grammatophora there 

 is one at each pole. 



The author maintains that the centrifugal growth of the cell-wall is 

 not due to the extraneous protoplasm, but, like the centripetal growth,, 

 is completed within the cell. 



Polymorphism in the Chlorophyceae.f — Herr T. Hedlund has culti- 

 vated about twenty species of aerobic Chlorophyceas in the following 

 method. The alga is placed on a transparent lamella of the periderm 

 of the birch only a few cell-layers in thickness, which is then replaced 

 in its natural position on the tiee, removed from time to time, and 

 examined under the Microscope. He finds in this way that alterations 

 in the external conditions — light, moisture, temperature, &c. — will often 

 cause great variations in a species in a single generation; but that not 

 unfrequently a return to the original form will take place in the second 

 generation, even when the new conditions still remain. Such variations 

 he terms " modification-forms." A single species may thus include 

 forms which produce and forms which do not produce gonids ; forms 

 with smooth and forms with spiny membrane ; spherical forms and 

 spindle-shaped forms with rounded ends ; forms with one and forms 

 with two chromatophores, &c. Modification-forms have been erected 

 into species in the genera Dactylococcus, Gloeocystis, Stichococcus, Pleuro- 

 coccus, Cyslococcus, Hormidium, and Prasiula. 



Development of Green Algae without Carbonic Acid Assimilation.^ 

 — Dr. A. Artari has tried a series of experiments on some green algae — 



* Ber. Deutsch. Bot. Gesell., xvii. (1.899) pp. 423-52 (2 pis. and 1 fig.). Cf. thi* 

 Journal, 1899, p. 308. 



+ Ofv. k. Vetensk.-Akad. Forhandl., 1899, pp. 509-35 (5 fi-s.). See Bot. Cea- 

 tralbl.. lxxxi (1900) p. 272. 



$ Bull. Soc. Imp. Nat. Mo&cou, 1899, pp. 39-47 (2 figs.). 



