THE ANGIOSPERMAE 



1487 



on cuticle for their protective material (Fig. 1360). Fatty cuticles occur both 

 between the integuments and on the inside of the inner integument. 

 Twenty days after pollination shrinkage of the fleshy integuments sets in. 

 The inner integument disappears so that the two cuticles come together. 

 The parenchyma of the outer integument is completely flattened and 

 finally only the outer epidermis, the crushed layer and the cuticles 

 remain. 



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Fig. 1360. — Asparagus officinalis. Sections of the developing testa. A, 8 days after polli- 

 nation. B, 20 days after pollination. C, Mature seed. {After Robbins and Bortlmick.) 



We have hitherto treated the testa as if it were unquestionably the pro- 

 duct of the integuments of the ovule, with occasional participation by the 

 nucellus or even the endosperm. There is evidence, however, that the 

 chalaza may sometimes play an important part. We have pointed out, in 

 the previous chapter, that the vascular bundle of the funicle usually ends in 

 the chalaza, occasionally splaying out into a few short ofl'shoots, but only 

 in few cases entering the outer integument, or prolonging itself as far as the 

 micropyle. Yet in many mature seeds integumental vascular bundles 

 occur, both in the outer integument and, in Dipterocarpaceae, in the inner 

 integument, or even in the perisperm, that is in tissue apparently of 

 nucellar origin, although nucellar bundles are almost non-existent in Angio- 

 sperms. It is difficult to account for the presence of these bundles in the 

 seed in any other way than by supposing that there has been a general 

 extension of chalazal tissues towards the micropyle to form a more or less 

 considerable portion of the testa. Indeed, in some cases, for example in 

 Canna, Ricinus and Eranthis, the integumental portion of the testa seems to 

 be limited to the region of the micropyle. The true condition in particular 

 cases is difficult to judge, without developmental study, inasmuch as the 

 tissue differentiation in the chalazal part of the testa is identical with that in 

 the integumental portion, just as the differentiation in the raphe portion 

 of the testa is the same as that in other portions, though the raphe properly 

 belongs to the funicle rather than to the integuments. Upgrowth of the 

 chalaza in this fashion has its parallels in the Gymnosperms and in the 

 Pteridosperms and has therefore a long history behind it. It is no new 

 thing in the Angiosperms but is something that might be expected. Very 

 little information exists about it and developmental studies of seeds in such 

 families as Nymphaeaceae, Magnoliaceae, Fagaceae, Euphorbiaceae or 

 p 



