The Mickoscofe. 291 



methods will be found preferable where such delicate tissue is to 

 be embedded. But for objects that will withstand this process 

 of inflltratien, the paraffin method has many advantages over 

 other methods. Embedded in paraffin, objects are held firmly 

 and may be preserved as long as desired without further atten- 

 tion. 



For embedding mature seeds, I have found nothing that was 

 equal to paraffin. The texture of the seed is often very dense 

 and offers much resistance to a knife. For this reason I found 

 it better t® use the harder grade of paraffin. A second serious 

 difficulty that was met with in embedding seeds was the fact 

 that there was little if any tissue connecting the embryo * with 

 the seed coats. Thus it would often happen that just as the sec- 

 tions were being taken through the middle of the seed (the most 

 valuable ones are those near the centre), the embryo would 

 leave the coats and the whole series be spoiled. The inner sur- 

 face of the inner coat in many seeds is highly polished, and as 

 soon as there is nothing to retain the embryo but its adhesion t© 

 the coat it will loosen. The paraffin does not seem to hold the 

 two together as might be expected. It was suggested that in 

 order to soften the tissue, and thereby make it more susceptible 

 of infiltration, it would be well thoroughly to soak the seeds in 

 water before hardening in alcohol. This was tried, and there 

 was a great improvement in the result. Fewer of the sections 

 went to pieces after they were transferred to the slide, and the 

 parts kept their respective positions much better. 



In order to study the microscopic structure of seeds, much 

 more satisfactory results can be obtained if the sections are 

 kept in series. It is often necessary to have two or more suc- 

 cessive sections before a correct idea can be obtained. 



The method used is a modification of the one used and taught 

 in the histological laboratories of Cornell University. In its 

 practical application it is as follows : In choosing seeds to sec- 

 tion great care is taken to get those which are well filled. This 

 precaution is especially important, as many seeds never develop 

 more than the coats of the enveloping ovary layers. If a seed 



* The term ' ' embryo ' ' is used here, where on some accounts it would be 

 better to use the word nucleus. The embryo is often but a very small part 

 of the substance contained within the seed coats. If the word nucleus is 

 used it might be confused with the histological significance of the term. 



