116 PALMELLACE^. 



Order XIII.*— PALMELLACE^. 



Palmellacece, Harv. Man. Ed. 2, p. 234. Pahnellece, Dne. Class, p. 31. Endl. 

 2,rd. Supp. p. 10. Kiitz. Phyc. Gen. p. 166. Hass. Brit. Fr. Wat. Alg. p. 306. 

 Lindl. Veg. King. p. 18. Kutz. Sp. Alg. p. 196. Berk. Crypt. Bot. p. 114. Thtmites, 

 in An. Nat. Hist. 2ndSer. vol. 2, p. 312, aiid vol. 3, p. 243. Part of TJlvacew, Harv. 

 Man. Ed. 1, p. 169. Part of Nostochinece, Ag. Syst. p. 13. Harv. in Hook. Br. 

 /. 2,p. 394. 



DuGNOSis. Green or red, orange or yellowish, fresh-water Algae, composed of separate 

 or aggregated (hut not united) globose or ellipsoidal cells, free, or lying in a gelatinous 

 matrix ; sometimes sti^jitate. Propagation by division of the endochrome. 



Natural character. The plants of this family are the simplest in organization of 

 any of the great class of the Algse, and therefore fall to the lowest point of the scale in 

 the arrangement we have adopted. In them we no longer find any distinction of root 

 from frond ; most of them are amorphous masses of gelatinous substance, and only in a 

 few, as in Hydrurus, does the gelatine assume a tolerably definite form, and display 

 itself as a branching frond. The simplest of the group (Protococcus) consists of single, 

 isolated cells, strewn on the surface of the soil or of whatever object to which they 

 happen to attach themselves. These cells are globose or egg-shaped, have a hyaline, 

 often gelatinous coat, and contain a utricle filled with dense endochrome of various 

 colours ; sometimes green, but often red or orange. Of this character is the Red Snow 

 plant (Protococcus nivalis) which has attracted so much notice, from the accounts of 

 arctic travellers, and which may often be seen tinging the snows of Mount Blanc and 

 other snowy Alps with a pale roseate hue. The mode of propagation of this primordial 

 plant is as simple as its structure. The matter in the cell becomes condensed at 

 maturity, and then subdivides into 4, 8, 16, or more parts, on a quaternary scale of 

 increase ; each frustule acquires a new cell-coat while yet within the parent cell, and 

 when the process is completed, and all the endochrome of the mother cell has thus been 

 used up in providing for the progeny, the cell-coat bursts and a multitude of minute 

 cell-plants, similar in all respects to the parent except in size, are launched into the 

 world. These grow till they attain the dimensions of the parent, when a similar cell 

 division takes place ; and thus in a very few generations millions of new plants may 

 be produced from a few or even from a solitary original. As the process of growth and 



* Orders XI. Desmidiacece , and XII. Diatomacece are omitted in this work ; the American species having 

 been ah-eady pai-tially described and published by Professor Bailey, and the author not being supplied with 

 any new materials for publication. 



