AND THE EmIIRYO-SAC IN BlGXONIA VENU5TA 103 



Jished upon, species of AUiiini^ show reduction, or the indication 



of reduction, in tlie division of the initial cells ; and among dicoty- 

 ledons Hcllcborus foetichis and PodopJiylboji peltatii)n\ show the 

 reduced number of chromosomes during the formation of the axial 



row. 



Notes on Material and on Methods 



Material of Bignonia vennsta in quantit}' was secured from the 

 botanical conservatories. A single cluster of flower buds will give 

 many stages of development ; but when it is desired to have ma- 

 terial showing division in the pollen mother-cells, it is quite neces- 

 sary to examine an anther from each bud in order to avoid loss of 

 time in sectioning useless material. At first I experienced some 

 difficulty in securing such stages from collections made during 

 bright forenoons. On examining a number of buds it was easy 

 roughly to locate the beginning of division by the bursting of the 

 calyx lobes. By this means, during the early afternoon I located 

 and marked about twenty buds apparently just preceding division. 

 Haifa dozen buds of the same stage were then examined as checks, 

 and found to be just preceding the formation of the spindle. At 

 ten o'clock tlic following morning the marked buds were examined 

 and all of them had passed tlirough both divisions of the pollen 

 mother-cells. This one experiment, together with previous fail- 

 ures, led me to suspect that these divisions were very rapid in this 

 plant, and probably occurred at night. Material collected at night 

 did yield many divisions, but at noon on a cloudy day I likewise 

 secured all material desired of these stages. Nevertheless, it may 

 be of interest that these divisions were never found during bright 

 days. 



Fixing, embedding, etc. In general, the material studied was 

 fixed in Flennning's solution, as this proves so generally satisfactory 

 in work with plant tissues. The mixture is substantially Flemming's 

 strong solution, and the formulae are giv^en in percentages, and as 

 made up for y> gram osmic acid : 



^ Strasburger, Ueber Kern uiid Zellteilung iin Pflanzenreicb, Histol. Beitr. II. L, 



243 



■j^Mottier, D. M., Ueber das Verhnlten dcr Kerne bei der Entwickelung des Em- 

 bryosacks und die Vorgilngebei der BefruL-litung. Jahrb. wiss, Bot. 31: 125-158. 1897. 



