738 
Journal of Agricultural Research 
Vol. XXVII. No. io 
hensive and helpful as possible, representatives of as many types of 
raspberries as could be procured were selected with special reference to 
the economic importance of the groups, their botanical relationship, and 
their possible value in breeding. 
MATERIAL AND METHODS 
The plants from which buds were taken were grown at the Bell Horti¬ 
cultural Field Station, Glendale, Md., and at Arlington Experiment Farm, 
Rosslyn, Va. 
Material was collected during the last two weeks of May, in June, and 
again in September and October (1923). Buds were killed in weak chromo- 
acetic solution, and in Bourn’s killing mixture, both of these being quite 
satisfactory. 
All material was imbedded in nitrocellulose, this medium having been 
found very satisfactory for this type of investigation. The buds were 
sectioned about 15 micra thick so as to have uncut nuclei for study. 
Heidenhain’s haematoxylin was used for staining chromosomes. The 
mother cells were studied by the use of 2 mm. and 1.6 mm. Zeiss apochro- 
matic lenses and No. 12 and 18 compensation oculars. 
Pollen counts were made from anthers that had not dehisced. Plate 
1, A, shows a bud in the stage of development usually chosen. The 
anthers were crushed in water on a glass slide and all plump grains 
counted as good. As a rule, the count was made from 100 grains only 
and the percentage of good pollen is, therefore, only approximate. Ger¬ 
mination tests and special technique are necessary for a final test. 
HISTORICAL AND CYTOLOGICAL DESCRIPTION 
For convenience, the classification of Focke has been followed, for the 
most part, and the results have been presented in sections and series as 
given in ‘ ‘Species Ruborum’ ’ (8 ). The few polyploid forms, however, have 
been segregated and discussed after the review of the diploid forms. 
Brief historical descriptions of many raspberry species and garden 
varieties are first given. The inconsistency existing in the nomencla¬ 
ture ol horticultural raspberry and blackberry forms makes it necessary 
to include the available history of each species and variety used in this 
study, since in this way the identity of the material will be established 
more definitely. These descriptions, which we regret are incomplete, are 
followed by the results of morphological and cytological studies of pollen 
and pollen formation. 
Table I presents a summary of the pollen counts and the chromosome 
number and behavior during the pollen tetrad formation of the species 
and varieties studied. Plates 2 and 3 show drawings of heterotypic 
prophases selected from type species, varieties, and hybrid forms. 
