2 8 FIRST GROUP. THALLOPHYTES. 



to be a reduction-product of the latter, and to which he gives the name of chloro- 

 rufin \ 



The cell-structure and manner of life vary much among the Chlorophyceae, but 

 the structure of the thallus never reaches so high a stage with them as with the. 

 Phaeophyceae. Many species are unicellular, others consist of cell-filaments or single 

 cell-surfaces ; the Siphoneae exhibit unicellular tubular filaments which often attain 

 to large dimensions, and have numerous nuclei in their protoplasm. Most of the 

 Algae of this subdivision live in water; a few only are found in spots that are 

 occasionally moistened with water, as Chroolepus, which grows on the stems of 

 trees and on stones, and has the peculiarity, that its vegetative cells assume the red 

 colour mentioned above. A certain number of Chlorophyceae live in cavities of 

 plants of a higher order, a mode of life adopted by them chiefly for the sake of 

 shelter, and therefore named by Klebs ' Raumparasitismus V Thus the zoospores of 

 Chlorochytrium make their way into the tissue of species of Lemna, by inserting a 

 process between the walls of two opposite epidermal cells and thus opening a passage 

 for themselves into the substance of the plant, where they develope into a green 

 spherical body. Other Protococcaceae make a home in the tissue of the leaves of 

 various dicotyledonous water-plants. Filamentous Algae also have been known to 

 adopt this mode of life. One of the Siphoneae, Phyllosiphon Arisari*, lives in the in- 

 tercellular spaces of the leaf of Arisarum vulgar e> and moreover draws nourishment 

 from the cells of the leaf, for the chlorophyll is consumed in the cells contiguous to 

 the intercellular spaces which are occupied by the Phyllosiphon^ and of their proto- 

 plasm there remains ultimately only a thin wall-layer. This then is a case not only 

 of ' Raumparasitismus/ but of true parasitism, such as is known in the case of other 

 chlorophyll-containing organisms ( Viscum, Thesium, and some species of Rhinanthus). 

 It may be remarked that the leaf-cells of Arisarum remain turgescent almost, up to 

 the moment when they have completely parted with the substances which they 

 contained. 



Classification of the Chlorophyceae*: 



1. Siphoneae (Coeloblastae). Thallus composed of tubes, undivided by septa, and 

 lying free or interwoven with one another, and often attaining a high degree of 

 morphological differentiation, as in Caulerpa with organs resembling stem, root and 

 leaves. Sexual propagation the result either of conjugation of swarming gametes of 

 similar form (Acetabularia, JBotrydtum], or of fertilisation of an oosphere ( Vaucherid). 

 The species live on land, and in fresh and salt water. 



2. Volvocineae. Unicellular, or forming a pluricellular family. They have this 

 peculiarity, that their cells move about by means of cilia during the vegetative stage ; 

 the families also which consist of a number of variously arranged cells have the power 

 of free movement. Sexual propagation isogamous or oogamous. 



3. Protococcaceae. Unicellular stationary Algae, isolated or united into families. 

 Sexual propagation isogamous (Hydrodictyon] or oogamous. 



1 Rostafmski, Ueber den rothen Farbstoff einiger Chlorbphyceen, &c. (Bot. Zeit. 1881, p. 461). 



2 [If a special term is necessary for such endophytic plants we may designate them 'aulophytes.'] 



3 Kiihn, Ueber eine neue parasitische Alge Phyllosiphon Arisari (Sitzungsber. der naturf. Ges. 

 zu Halle, 1878). Just, Phyllosiphon Arisari (Bot. Zeit. 1882, Nr. u if.). 



* [Klebs, Ueber d. Organis. ein. Flagellatengmppen u. d. Beziehungen z. Algen u. Infusorien 

 (Unters. aus d. Bot. Inst. z. Tubingen, I. Heft 2, 1883). See also Biol. Centralbl. IV. (1883).] 



