TIIK ALGJE. 



103 



tubes from another tilament. (See Fig. 57, (7, e.) These 

 spores are produced by parthenogenesis. 



13. Place some freshly gathered vigorous Spirogyra in 

 a refrigerator over night. In the early morning examine 

 for the division of the cells by the asexual process. This 

 division takes place, under natural conditions, at about 

 the middle of the night. Cold delays the process. Make 

 drawings showing as many different stages as are found. 



References for Reading. Parker's "Elementary Biology," pp. 149- 

 200; Goebel's "Classification of Plants," pp. 48-50; Bennett and 

 Murray's " Cryptogam ic Botany," pp. 264-266; Vines' "Text-Book 

 of Botany," pp. 244-246; Sachs' "Physiology of Plants," pp. 727, 

 728 ; Huxley and Martin's " Practical Biology," pp. 396-407 ; Arthur, 

 Barnes, and Coulter's "Plant Dissection," pp. 33-42; Bessey's "Essen- 

 tials of Botany," pp. 122, 123; Campbell's "Structural and Systematic 

 Botany," pp. 30-33; Dodge's "Practical Biology," pp. 51-61; Boyer's 

 "Elementary Biology," pp. 121-124; Strasburger and Hillhouse's "Prac- 

 tical Botany," pp. 207-209, 246, 247 ; Bower's " Practical Botany," pp. 

 442-446. 



The Mesocarpeae are 

 distinguished from the 

 Zygnemese by the arrange- 

 ment of the chlorophyl 

 in straight bands in the 

 longitudinal direction of 

 the cell rather than in 

 spiral coils and dumb-bell- 

 shaped figures. The sex- 

 ual multiplication is by 

 a process of conjugation 

 similar to that of the 

 Zygnemese ; the asexual 

 reproduction is by the 

 separation and subsequent 

 fission of the cells of the 

 filaments, 



FIG. 58. Mesocarpus. a, conjugating 

 cells ; 6, vegetative cells. 



