276 



BOTANY. 



the pericarp, in addition to tlie 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" {d, 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 

 is consummated only 

 when the connecting 

 tube comes in 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 

 and interesting one, but un- 

 fortunately it cannot be 

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

 fact tliat 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 phycoerythrine the 

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

 which had been masked by the brigliter 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 Algse of the United States," 1876, published in the 



Fig. 186. — Ihtdreanaya pvrpvHfera. tr, tricho- 

 gyne, with gpermatozojde altnched ; cl, connecting- 

 tube which grows out from below the basse of the 

 trichogyne, and comes in contact with the fertile 

 branches, /, f ; ct', young connecting-tube.— After 

 Thurct and Bornet. 



