26 ACADEMIC BOTANY. 



Here the reproduction is of two kinds. Sometimes a mother-cell 

 is formed at the end of one of the hranches'by the concentration of 

 the chlorophyl or protoplasm, and the development of a partition 

 (torus), which separates it from the main plant. A spore is formed 

 by this mother-cell, unaided ; at maturity the mother-cell bursts, and 

 the spore escapes as a zoospore (Fig. 1, D). Sometimes two cells of 

 different forms appear, near, to each other, on the same branch ; these 

 have already been described (15) ; and the union of their contents, as 

 we know, is called Fertilization. 



46. Parentage.^ — There are, then, two modes of parentage 

 or reproduction, each exhibiting two forms. 



A. Single Eepeoduction : 

 /. Cdl-Division, or Fission — ^ 



Cryptogamia, spore. 

 II. Parthenogenesis — Phan- 

 erogamia, seed. 



B. Dual Reproduction : 



I. Conjugation — Cryptoga- 1 Produced by the union of 



gamia, spore. J two similar cells. 



IL Faiilization-Crypi<,ga- 1 produced by the union of 



-rii P ■ . J 1 two dissimilar cells. 

 Phanerogamia, seed. J 



Produced and developed 

 in a mother-cell with- 

 out foreign aid. 



LESSON VI. 



THALLOGENS FINISHED. 



47. Many-celled plants ; Tballus. 48. Olive Seaweeds. 49. Wracks. 

 50. Bed Seaweeds. 51. Fungi. 52. Mildews. 53. Moulds. 54. 

 Mushrooms. 55. Fungi described. 56. Lichens. 57. Thallogenous 

 Growth. 



47. Many-celled plants. Thallus. — We next find plants 

 forming cells as usual, by division ; but the cells remain 

 united, forming cellular tissue, which spreads into leaf-like 

 shapes, often branching and simulating stems, boughs, 

 leaves, and fruit. This tissue is called a TliaUus, as we 

 have already learnt in Lesson II. (15 a); it is also called a 



