Observations on the Structure of the Seed in 
the Capparidaceae and Resedaceae. 
BY 
MATTHEW YOUNG ORR, 
Assistant in Laboratory, Royal Botanic Garden, Edinburgh. 
With Plate CLXVIII. 
THE presence of a specialised layer of distinctively marked 
elements, completely investing the embryo, is a characteristic 
feature in the seeds of certain Capparidaceae, and, in dissections 
of the seed of these genera which have been investigated, it 
has the appearance of a third seed-coat, internal to the fibrous 
tegmen. 
The configuration of the thickened walls of the elements 
composing this enveloping sheath has been described elsewhere,* 
and it has been shown that, apart from its physiological signifi- 
cance, the localisation of the thickening bands on the periclinal 
or anticlinal walls of the constituent elements is capable of being 
regarded as a diagnostic feature, distinguishing the seeds of the 
two tribes of the Capparidaceae. 
In the seeds of the Cleomeae the thickening is confined to 
the periclinal walls of the cells, and is in the form of delicate 
striations, which, when seen in surface view, produce the effect 
of finger-prints, such as are made use of in criminology. In the 
seeds of the Cappareae, on the other hand, the thickening bands 
are found only on the anticlinal cell walls, and present a totally 
different appearance when viewed under the microscope. This 
distinction is suggestive of the possible value of the features of 
the sheath from a systematic point of view. 
Records of the occurrence of similarly constructed tissues in 
seeds are rare, but it was thought that, if the methods adopted in 
the investigation of the seeds of the Capparidaceaewere applied to 
the seeds of allied families, details of structure which had hitherto 
been overlooked might be disclosed, and such features might 
possibly have some bearing on the phylogeny of the family. 
On these lines, an examination of the seeds of representative 
genera of the Resedaceae was first undertaken, and it was 
observed that the tissue surrounding the embryo, which has the 
appearance of a third seed-coat, possessed those special features 
which characterise the corresponding tissue in the seeds of 
certain Capparidaceae. : 
* See p: 240. 
