54 BOTANICAL GAZETTE [jULY 



Lyon, Florence, The spore coats of Selaginella. Box. Gazette 40:285. 1905. 

 N£mec, B., Ueber die Bedeutung der Chromosomenzahl. Bull. Int. Acad, 



Sci. Boheme. 1906. 

 RoSTOWZEW, S.J Recherches sur Ophioglossum vulgatum, (Bot. Centralbl. 



50:364. 1892.) 

 Russow, E., Vergleichende Untersuchungen betreffend der Histologie dcr vege- 



tativen und sporenbildenden Organe und Entwickelung der Sporen der 



Leitbundelkryptogamen. Mem. Acad. Sci. St. Petersburg VII. 19: no. i. 



1872. 

 Stevens, W, C, Spore -formation in Botrychium virginianum. Annals of 



■ 



Botany 19:465. 1905, 

 WiLLE, N,, Ueber die Entwickelungsgeschichte der Pollenkorner der Angio- 

 spermen und das Wachstum der Membranen durch Intussusception, Chris- 

 tiania. 1886, 



EXPLANATION OF PLATES III AND IV 



All figures were drawn with the aid of a Bausch and Lomb camera and 

 Zeiss apochromatic objectives and compensating oculars, and reduced one -half. 

 Figs, i-y and fig. j2 were drawn under a low -power dry lens, the others under 

 1.5™"^ immersion. 



PLATE III 



Wall 



turn one-layered except at left. X300. 



Fig. 2. Wall four- or five-layered; tapetmn two-layered; sporogenous tissue 

 beginning to break up into irregular blocks and to separate from the tapetum. 

 X 300. 



Fig. 3. General view of about one-half of a sporangium, showing four or five 

 layers in the wall; two-layered tapetum; sporogenous tissue broken up into 

 irregular blocks; the regular two-layered tapetum is restricted to the left of the 

 figure; in the remaining part it is difficult to distinguish it from the sporogenous 

 tissue; i is last wall formed, X 123. 



Fig. 4. Tapetal Plasmodium penetrating amongblocks of sporogenous tissue; 



tapetal nuclei mainly around periphery; blocks of sporogenous tissue quite 

 irregular. X300. 



Fig. 5, An unusually thick tapetum and more regular blocks of sporo- 



FiG. 6 



fig. 4. X 300. 



y 



sporogenous 



show early indications of formation of slit for dehiscence. X300. 



FiG. 7. Mature wall showing longitudinal section thr 

 inner cell layers broken down. X123. 



Fig. 8. A sporogenous cell lacking about two divisi 

 from sporangium with a three-layered wall. Xooo. 



been 



ing for the sake of clearness, X900 



