136 



BROOKLYN BOTANIC GARDEN MEMOIRS 



that are sacrificed in order that the epidermis may be broken open 

 (Text-fig. 2). The true basal cells now grow out through the buffer 

 cells, forming a club-shaped bud which soon becomes binucleated. 

 These nuclei divide and the stalk is cut off; later three pairs of nuclei 

 can be seen and the wall is formed between the two cells of the teleuto- 

 spore (Text-fig. 3). Quite mature spores can be found along the line 

 where the epidermis first ruptures and all stages in their development 

 can be seen further back. 



Fig. 2. A portion of a sorus of G. transformans showing two rather pointed 

 buffer cells forcing epidermal cells aside, fragments of the walls of the epidermal 

 cells lie just above the buffer cells at the right. Four young teleutospore buds 

 are visible. 



Fig. 3. Teleutospore of G. transformans. 



The gametophytic stage on Aronia may sometimes attack the 

 young stem, giving rise to an irregular herbaceous gall, which becomes 

 covered with horn-like projections from which the aecidia arise. 

 If such a plant is kept in the greenhouse all winter, aecidiospores will 

 continue to be formed in some cases for several months after the 

 leaves have fallen from the plant. These spores are regularly bi- 

 nucleated and possess 7 or 8 germ pores irregularly distributed (PI. I, 

 Fig. i). The spores germinated on agar or water frequently form a 

 swollen pouch near the tip of the germ tube. The nuclei of the spore 

 push through the germ pore, apparently one closely following the other 

 (PI. I, Fig. 3). At the next stage we find two nuclei lying in the 

 germ tube just outside of the pore (PI. I, Fig. 4). These nuclei then 

 migrate further out into the tube and come to lie in the swollen pouch 

 (PI. I, Fig. 5) where they presumably divide conjugately, since many 

 cases have been observed where there were four nuclei, in pairs, lodged 

 in this portion of the tube (Fig. 6). The germ tube now elongates 

 rapidly and branches freely at the tip (Fig. 8). The four nuclei move 

 forward and may lie along the tube in a row in the wider portion at 

 the end or they may be distributed, one nucleus in each branch, or 



