244 Ml' Gregory, Note on the Histology of the Giant 



As a further test drawings were made of the six largest nuclei 

 to be found in this layer in one section passing through the ovule 

 in an approximately median plane. The result is shown m 

 fig. 8, in which the left hand row represents nuclei of the 

 ordinary form, the right hand row nuclei of the Giant. The 

 difference here is obvious. Lest chance should have favoured the 

 Giant, further drawings were made of the ordinary form, choosmg 

 the largest nuclei which could be found in the serial sections of 

 some four or five ovules which were mounted on the same slide. 

 The six largest of these are reproduced in fig. 9; it will be noticed 

 that they are rather smaller than the six nuclei drawn from one 

 section of one ovule of the Giant form. 



Evidence has been given above which I think clearly suggests 

 the existence of a difference in size between the nuclei of the 

 Giant and ordinary forms. It remains to compare the size of 

 entire cells. It is very desirable that in instituting this com- 

 parison measurements should be made of the living pollen mother 

 cells and living pollen grains, but at the time when material of 

 this kind was available the trend which this work has since taken 

 was unforeseen. Microtome sections of growing tissues are, at the 

 best, unfavourable for making measurements of entire cells, and in 

 default of measurements of isolated cells such as might be pro- 

 vided by the pollen, I have had recourse to hand sections of the 

 living tissues of the stems and petioles. Transverse sections were 

 cut from the living material and mounted in water, so that no 

 disturbance due to shrinkage was possible. Care was taken to 

 avoid any disturbance due to the drag of the razor m cutting. 

 Measurements of the diameters taken when the sections were cut 

 show that the stems and petioles of the Giant are thicker than 

 those of the ordinary form, the proportional diflference being about 

 4 to 127 of the diameters, or of the same order of difference as 

 that found in the size of the nuclei. The size of the individual 

 cells encountered in such sections is naturally very divergent, but 

 by drawing the outlines of the cells to exactly the same scale 

 the difference in their size in the two forms is strikingly shown. 

 A number of drawings were made in this way from sections ot 

 various comparable regions of the stems and petioles. Two pairs 

 of these drawings are shown in figs. 10 and 11, and 12 and 13. 

 The figures represent sections, chosen at random from a number 

 floating in a watch glass, of the main flowering stems of the two 

 forms, in each case taken half way between the base of the stem 

 and the lowest umbel of flowers; figs. 10 and 11 show the region 

 of the pith, and figs. 12 and 13 the cortical region, m the ordinary 

 and Giant respectively. It will be noticed— what has been found 

 to be the case in all the sections made— that the cells of the Giant 



