DEPARTMENT OF BOTANICAL RESEARCH. 105 



Seeds of Opuntia fulgida were germinated at Baltimore to seedlings 

 a centimeter long. The germination of these seeds has not hitherto 

 been reported, so far as is known. It evidently occurs but rarely in 

 the field and was accomplished in the laboratory only after part of the 

 seed coat had been cut or filed away. Careful search among the 

 fruiting plants of 0. fulgida at Tucson in April failed to reveal any 

 plantlets that could be shown to have arisen either from seeds or from 

 fallen fruits. All the young plants seen had evidently come from the 

 areolse of fallen vegetative joints. A search in September 1915 led to 

 the discover}' of a dozen rooted fruits which evidently had sprouted 

 during the summer rains. Thus, though fallen fruits readily give rise 

 to new plants in the greenhouse, they apparently do not do this fre- 

 quently in the field. By following the fruit development of 0. fulgida 

 through the whole summer it was found that four, or possibly more, 

 generations of fru,its may be added to one of its fruit chains in a single 

 growing-season. The primarj^ flower of the season, developed in spring 

 from a persistent fruit of the preceding year, may form secondary flowers 

 from its own areolae. These secondary flowers open several weeks after 

 the primary ones and may themselves give rise to tertiary flowers, and 

 the latter in turn often form flowers of the fourth generation for the 

 season in August. In other cases only one or two fruits, or sometimes 

 none, are added to a chain during a whole season. Hence it is evident 

 that the longest chains seen, made up of 12 or 14 fruits, may be formed 

 in three or four j^ears or may take eight or ten. 



A study of the behavior of the fruits of other species of Opuntia 

 growing about Tucson and at Chico, California, showed that there are 

 several species in which the fruits may persist for one or two years 

 attached to the parent plant, though none forms such large fruit- 

 clusters as 0. fulgida. Thus in 0. spinosior, 0. arbuscula, and in certain 

 plants of 0. versicolor, at Tucson, many single, persistent normal fruits 

 and occasionally chains of two or three were found in April. In several 

 of the flat-jointed opuntias about Tucson and in most plants of 0. 

 versicolor no attached fruits were found in April 1915 except abnormal 

 ones that harbored the pupae of the cactus fly, Asphondylia opuntice. 

 Most of these galls had the form of hypertrophied, unopened flower- 

 buds. In these the red of the petals still persisted and, aside from being 

 twice the normal size, they appeared as if just ready to open. They do 

 not open, however, but in May the pupa-cases protrude through the 

 wall of the fruit, the flies escape, and by June most of the galls have 

 withered and dropped. A few only of the less hypertrophied buds 

 formed flower-buds from their areolae in 1915. In only two or three 

 instances had a persistent gall given rise to a vegetative joint. When 

 these galls of 0. versciolor were planted beside the fruits of 0. fidgida on 

 soil in the greenhouse, they did not, like the latter, give rise to vegeta- 

 tive shoots, but withered and decayed. 



