5 1 o Campbell . — Development of Geothallus tuber osus. 
Fig. 32. Cross-section of the neck of the archegonium, x 300. 
Fig. 33- A four-celled embryo, enclosed in the venter of the archegonium, 
x 300. 
Fig- 34. Longitudinal section of an older embryo, x 300. 
Fig. 35- Similar section of an older embryo, showing the calyptra, x 300. 
Fig. 36. Two transverse sections of an embryo of about the same age as that 
shown in Fig. 35, x 300. a is the apical region ; b is lower down. 
Fig. 37. A section through the upper part of a young sporogonium, after the 
separation of the spore-mother-cells, x 50. 
Fig. 38. A spore-mother-cell and two sterile cells from the same sporogonium, 
X 300. 
Fig. 39. A germinating spore, x 100. 
Fig. 40. Apex of very young thallus, showing the two-sided apical cell, x ; 
g, the germ-tube ; x 300. 
Fig. 41. A somewhat older stage, x 300. 
Fig. 42. Young plant still showing the germ-tube, g, and spore, sp , x 40. 
X, the growing-point of the thallus. 
