276 



BOTANY. 



the pericarp, in addition to the parts found in the latter 

 genus. 



369. In the genus Dudresnaya there is a curious and 

 complicated sexual process. After the fertilization of the 

 trichogyne, a long " connecting tube" (ct, Fig. 186) grows out 

 from beneath the trichophore, and comes in contact with the 



fertile branches (/, /, 

 Fig. 186), to the ter- 

 minal cells of which it 

 becomes closely applied. 

 These fertile branches, 

 which grow as lateral 

 branches on the same 

 plant as the trichogyne, 

 are the true female or- 

 gans, and fertilization 



.^ y UL^*V3f ^->V\\ 1S COnSUmmated 0nl J 



\ }S fx?j^~-^~-^ p7 ) ) + when the connecting 

 / / rH/ ^^^N>4>v tu ^ e comes * n contact 



and coalesces with 

 them. The result of 

 this curious process is 

 the production of a spo- 

 rocarp on each fertile 

 filament. 



(a) This class is a large 



brancfies, /, f ; ct'. young connecting-tube. After and interesting one, but un- 



fortunately it cannot be 



studied readily except near the seaside, and even then, from tlie 

 fact that the species mostly inhabit the deeper waters, it presents many 

 difficulties. The plants are mostly red or violet in color, although this 

 is not due to the absence of chlorophyll. The red color is due to the 

 presence of a pigment (pliycoerythrine), which is soluble in cold fresh, 

 water ; its solution is carmine-red in transmitted light and reddish yel- 

 low in reflected light. Upon extraction of the pliycoerythrine the 

 plants are found to be green from the presence of the chlorophyll 

 which had been masked by the brighter pigment. 



(6) There are many orders in this class, the following of which are 

 represented in the United States.* 



* The sequence of the orders is that given by Dr. Farlow in his 

 " List of the Marine Algae of the United States," 1876, published in the 



tr, tricho- 

 gyne, with epermatozoid s attached; ct, connecting- 

 tube which grows out from below the base of the 

 trichogyne, and comes in contact with the fertile 



Fig. 186. Dudresnaya piirjnirtfera. 

 :, with epermatozoul 8 attached; ct, ( 



