THE WEIGHT OF THE EMBRYO 407 



grain, gave similar proportions for the two methods, the size 

 of the embryo, whether obtained from the actual seed or from 

 the illustration, being about -^ of that of the kernel. In this 

 case the proportional weight of the seed-coats was taken as 

 one-third of the total weight of the seed, which left -02 grain 

 as the weight of the kernel. I was therefore dealing with an 

 embryo which weighed not more than ^^ ^^^ part of a grain. 

 From the case of the Aquilegia seed to that of the minute 

 seed of a rush (Juncus) the step was not a very difficult one. 

 Having found that about 5500 seeds of Juncus communis went 

 to make a grain, I had to allow for the weight of the seed- 

 coats, which, judging from the figures and from my own 

 examination of the seed, was relatively much less than with a 

 seed of Aquilegia, so I placed it at about one-fifth of the seed's 

 weight. The weight of the embryo was then calculated to be 

 about one-tenth of that of the kernel, and from these data the 

 following results were obtained : — 



i Entire seed ^^g^ grain or •00001 18 gramme. 

 Juncus communis I Kernel ^sVs jj "0000094 55 



(Embryo ^^J^ „ -0000009 » 



In this manner, therefore, the minutest of embryos are 

 shown to be within reach of the balance. Whilst nearly 

 70,000 of the embryos of Juncus communis are required to make 

 a grain, nearly 200 of them placed in line will make an inch, 

 and nearly 8 will make a millimetre, the length of the embryo 

 being one-third that of the seed, which, according to my 

 measurement, is 0*4 millimetre long. 



With these preliminary remarks I will now give in tabular 

 form the results of my observations on the weights of the 

 embryos of albuminous resting seeds in the case of more than 

 fifty plants. They are arranged in the order of the embryo's 

 relative weight as a portion of the kernel. The indications 

 supplied by such an arrangement are full of suggestiveness, 

 and are especially discussed in the remarks that follow the 

 table, as well as in the last paragraph of the chapter. 



