786 SUMMARY OF CURRENT RESEARCHES RELATING TO 



forms the nervation of the leaves ends in a small projecting point or tooth, 

 and in addition to this presents another small tooth pointing downwards 

 below the apical tooth. This is the case in Bhyncostegium striatum. 

 It. rusciforme, Brachythecium salehrosum, B. velutinum, B. albicans, and 

 B. reflexum. 



Analogous variations in Sphagnacese.* — M. C. Jensen states that in 

 no other genus of mosses is the tendency of the individual species to vary- 

 more marked than in Sphagnum. It is not always possible to recognize the 

 cause of these variations. Water appears to exercise the chief influence, 

 then light or shade, and in some cases the temperature of the soil. The 

 organs of the plant liable to variation are, firstly, the leaves, and then the 

 branches, whether sterile or fructiferous. If the plant grows entirely in 

 water, all the parts become larger and longer. These variations the author 

 designates by the term formse immersse. Under the direct influence of the 

 sun's rays the plants become more compact {form.se compactse et strictse). If 

 the plant grow in the shade, it becomes more robust, and the leaves squarrose, 

 {formse squarrosulse). The author also designates certain variations as formse 

 falcatse, formse homophyllse, and formse tenellse. 



By taking various species of Sphagnum, and tabulating them under the 

 above divisions, the variation of the species taken can be seen at a glance. 

 Take, for instance, Sphagnum acutifolium Ehrb. This species is represented 

 in all the divisions, but especially well in formse tenellse and compactee. In 

 the first could be cited var. fusca Sch., tenuis Braithw., rubella Wils., and 

 gracilis Euss. ; and in the latter, var. arcta Braithw., congesta Gravet, and 

 Schimperi Warnst. A forma homophylla also occurs, which might readily 

 be confounded with S. molle Sull. The form stricta is well represented by 

 the vars. stricta and strictiformis Warnst.; the formse immersse are rarer; to 

 this belong vars. plumosa Milde, and immersa Schleich., while var. squarrosula 

 Warnst. represents the formse squarrosulse. 



Algae. 



Classification of Algse.f — Mr. A. W. Bennett proposes some modifica- 

 tions in the existing systems of the classification of Algae (including the 

 chlorophyllous Protophyta), in accordance with their aflBnities. Too little 

 importance has, he considers, at present been attached to degeneration or 

 retrogression, which may be exhibited in the partial or complete suppression 

 of either the reproductive or the vegetative organs. 



He traces all the various forms of vegetable life to three lines of descent, 

 represented by three distinct kinds of cell-contents — colourless, blue-green, 

 and pure green. The first appears to originate in the Bacteria or Schizo- 

 mycetes, from which are derived the whole group of Fungi. The second 

 primordial type consists of unicellular organisms, in which the cell-contents 

 are composed of a pale watery blue- green endochrome diffused through the 

 protoplasm, without distinct chlorophyll-grains, starch-grains, or nucleus, 

 the Chroococcacese, the simplest form of the Phycochromacese or Cyano- 

 phycese, which attain their Iiighest development in the Nostochinese, includ- 

 ing the Oscillariacese, Eivulariacese, Scytonemacefe, and Nostocacese. To 

 them are probably related the Diatomacese, which the author regards as a 

 simple form of life, probably not nearly connected with the Conjugatse. 



The third series, or Chlorophyllophycege, is the only one which has 

 developed into the higher forms of vegetable life. It is characterized from 

 the outset by the cells possessing a nucleus, starch-grains, pure chlorophyll, 



* Eev. Bryol., xiv. (1887) pp. 33-42. 



t Joiirn. Linn. Soc. Lond.— Bot., xxiv. (1887) pp. i9-61. 



