ALGAE. CONFERVOIDEAE. 41 



Its resting cells (compare Chlorochytrium} produce zoospores, some smaller, 'imcro- 

 zoospores, others larger, macrozoospores^ which differ from each other in size only and 

 perish if they remain isolated. They must conjugate with one another to bring about 

 the commencement of a new generation ; a small male cell unites with a larger 

 female cell, and their union produces a zygoznospore, which however has but two cilia 

 because the small gamete with its cilia is swallowed up in the larger. If one of these 

 zygozoospores, which retain the power of movement for some time, encounters a leaf of 

 Lysimachia, it enters by a stoma and puts out a germinating shoot, which thrusts 

 apart the cells of the leaf and reaches the foliar vascular bundles ; there it developes 

 between the spiral elements, and its protoplasm gathers in its anterior extremity, 

 which is now separated by a septum from the empty portion and developes into a new 

 Phyllobium. Besides these gametes Phyllobitim possesses also zoospores which are 

 produced asexually in smaller resting cells, but which may be wanting. 



As regards the mode of life of these endophy tic Algae, we cannot attribute to them 

 any form of parasitism that implies the receiving of nutriment from the host, for these 

 Protococcaceae contain abundance of chlorophyll and can take up inorganic substances 

 from the surrounding water ; moreover they grow quite as well inside dead plants, and 

 appear to do no harm to their host ; they seek rather a sheltered place of growth and 

 are therefore called by Klebs ' Raumparasiten.' (Compare the endophytic Algae 

 of some of the Muscineae and of Azolla.} 



To the above may be appended a brief notice of the PALMELLACEAE, a group 

 of Algae the course of whose development is little known ; stages in the life of Confer- 

 voideae and Volvocineae resemble forms of the genus Palmella and have been 

 supposed to be genera and species of the Palmellaceae. The Palmellaceae are like 

 the simpler forms of the Protococcaceae in appearance, but their cell-walls produce 

 a mucilage and their cells multiply by bipartition ; to them belong Pleurococcus (see 

 under the Volvocineae), Palmella^ Hydrurus consisting of slimy branching filaments 

 which grow in mountain streams, and some others. 



4. CONFERVOIDEAE. 



The name Confervoideae or Confervaceae (Chlorosporeae) is given to certain 

 Algae living mostly in fresh water in which the thallus is either a cell-filament 

 or a cell-surface. Of the latter kind are the Ulvaceae, in which the thallus is either a 

 single layer of cells, as in Monostroma, or a double layer, as in Ulva, and is often of 

 some extent. The two layers of cells not unfrequently separate from one another, 

 and the thallus thus becomes hollow (Enter omorpha). In the rest of the Chloro- 

 sporeae the thallus is a simple or branched row of cells ; if a number of filaments 

 growing close together unite with one another, as in Coleochaete, they form a disk- 

 shaped thallus which grows at its margin. In many of the plants belonging to this 

 group, Siigeoclonium for instance, Ulothrix, Ulva and others, the thallus separates 

 into isolated cells which resemble the genus Protococcus, or the cell-walls becoming 

 largely mucilaginous the cells swell out into a spherical form and separate from one 

 another, and thus assume the condition and appearance of a Palmella^. The cells 

 thus isolated and imbedded in a jelly multiply by division. But these cells, to take 

 the instance of the palmella-state of Stigeoclonium^ do not produce a new Stigeoclonium 



1 Citnkowaki, Uber d. Palmellaceen-Zustand von Stigeoclonium (Bot. Zeit. 1876). 



