June i6, 1919 



Relation of Weather to Fruitfulness in Plum 



121 



Table III. — Rate of pollen-tube growth found in the plutn in controlled crosses in the 

 greenhouse and under orchard conditions 



UNDER GREENHOUSE CONDITIONS 



Cross. 



Minn. No. 10 "XMinn. No. 



12." 

 Minn. No. 10 K<P. Besseyi . 

 Minn. No. 12 '■XMinn. No. 



21.* 



Do 



Minn. No. 12 "XP. Besseyi . 

 Minn. No. 21 '•XMinn. No. 



Minn. No. 21 ''XMinn. No. 



10." 

 Minn. No. 6 " X Surprise . . , . 



Time. 



16 hours 



do 



9:30 a. m. to 3:30 p. m. 



17.5 hours 



ig hours 



51 hours 



69 hours 



6 days 



Tube growth in greenhouse. 



3^^ of style length. Cross 



sterile. 

 '2 of style length. 

 None. 



Vio of style length. 

 >4 of style length. 

 Do. 



Vio of style length. 



Full style length. None 

 fertilized. 



UNDER ORCHARD CONDITIONS. 



Minn. No. 21 '•Xopen-pol 



linated. 

 Minn. No. 35 ^Xopen-pol 

 linated. 



Do 



Minn. No. 12 ''Xopen-pol 

 linated. 



Do 



Minn. No. 12,^ selfed 



Do." 



Minn. No. 6, * selfed 



Manitoba, selfed 



P. Besseyi, selfed 



Surprise, selfed 



3 days after blooming . 



do 



6 days after blooming . 

 do 



10 days after blooming 



4^2 hours 



24 hours 



2 days 



8 days 



12 days 



6 days 



No tube growth. Rain 

 and frost. 

 Do. 



% of style length. 

 Do. 



Tube in embryo sac. 

 Tube just formed. 

 Vio of style length. 



Do. 

 X oi style length. 

 5 3 of style length. Ovule 

 ' aborted. 

 Vio of style length. 



» A cross between Burbank and Wolf. *> A cross between Abundance and Wolf. <^ See PI. 14, A. 



From Table III it appears that pollen-tube growth is relatively slow in 

 the plum and that the time required for the tubes to reach the ovary is 

 much longer than Sandsten estimated. Furthermore, it should be 

 emphasized that in the above table the maximum tube growth is gi\-en. 



It will be seen in the case of Miimesota No. 21 and No. 35 that there 

 was no tube growth three days after blooming when open-pollinated under 

 orchard conditions. The weather conditions previous to the time stigmas 

 were collected from these two varieties will be of interest here. Both 

 came into bloom on May 20, 191 7, which was clear, with a maximum 

 temperature of 62° F., with a slight rain in the evening, and a medium 

 wind the latter part of the day. At night the temperature fell and 

 there was frost. May 2 1 was cloudy, with a heavy rain accompanied by 

 a strong wind lasting from early morning up to 2 p. m. May 22 was cool 

 and clear, and the stigmas of these two varieties were collected in the 

 early forenoon. 



