140 BROOKLYN BOTANIC GARDEN MEMOIRS 



might lead to the formation of a greater amount of wood tissue such 

 as we find in the burl of G. hiseptatum. G. fraternum has almost con- 

 stantly 2-celled teleutospores, 3-celled spores are exceedingly rare. 

 In G. hiseptatum 3- and 4-celled spores predominate. I should be 

 highly gratified to learn that the change in environment from the leaf 

 to the stem, or more exactly from cortex to phloem, by the fungus 

 could bring about such a decided change in the structure of its spores. 



EXPLANATION OF PLATE I 



Gymnosporangium transformans 

 Stages in the Germination of the Aecidiospores. X 750 



Fig. I. A binucleated spore. 



Fig. 2. The germ tube has pushed out, the nuclei are still within the spore 

 and do not show appreciable change in form. 



Fig. 3. One nucleus is crowding through the germ pore, the other lies beneath. 

 The "pouch" is formed just back of the tip of the germ tube. 



Fig. 4. Both nuclei have escaped from the spore and lie just outside of the 

 germ pore. 



Fig. 5. Two nuclei lie in the expanded portion of the germ tube. 



Fig. 6. Four nuclei are plainly visible in the "pouch." The germ tube has 

 not begun the second stage of its growth. 



Fig. 7. Tip end of fully developed germ tube showing four nuclei in a row. 



Figs. 8 and 9. Other fully developed germ tubes showing a more pronounced 

 type of branching. 



Fig. 10. The germ tube has made about the maximum growth of which it is 

 capable under artificial conditions, a cross wall cuts off the main portion of the 

 granular cytoplasm at the forward end of the germ tube. 



