426 BOTANICAL GAZETTE [NOVEMBER 
A. Rudimentary alternation. 
- Rejuvenescence alone. 
II. Rejuvenescence with segmentation. 
Pisce i sata III. Segmentation alone. 
ypes. 
| B. Discrete alternation. 
C. Concrete alternation. 
Lp. Symbiotic alternation. 
“Recapitular alternation” refers to “the passage from the vegetative mul- 
ticellular to the reproductive unicellular condition ;’’ “heteroblastic develop- 
ment” refers to such an alternation as that of Chantransia and mature 
Batrachospermum forms; ‘sprout alternation” defines itself ; “homologous 
alternation” occurs where a potential gametophyte alternates with an actual 
gametophyte. These are styled “alteration types.” The true alternation types 
are defined as follows: “Rudimentary alternation,” defined above;” “ dis- 
crete alternation,” as in archegoniate plants (exclusive of gymnosperms); 
“concrete alternation,” as among the Floridez ; and “symbiotic alternation,” 
as in spermatophytes.—J. M. C. 
protoplasm which has collected there. Meanwhile the antheridial tube bs 
being formed, and after nuclear division a daughter nucleus passes to peas 
of the tube. When the tube reaches the dense mass containing the fe 
es 
can hardly be regarded as a reduction process, for 20 to 24 meee 
are found in the oosphere nuclei, and only 12 to 16 in the nucle! o 
oogonium.—W, D, M. 
4 Annals of Botany 10: 295, 1896. 
5 Annals of Botany ro: 107, 1896. 
