225 



Although we are unable to offer a finished investigation, 

 yet it seemed désirable to us to publisli what we hâve 

 seen. For Dasylirion blooms so seldom in Europe that for 

 us the chance of finishing our investigation is practically 

 zéro, while now at least attention has been drawn to it, 

 so that perhaps in the mother country of the plant some 

 one may feel inclined to re-examine it. 



Moreover the number of known cases of apugamy or 

 parthenogenesis is so small that there is every reason to 

 publish each new case. And flnally the material examined 

 by us présents some points which deserve attention for 

 spécial reasons. 



The fixed material was embedded in paraffin, eut with 

 the microtome and then stained, as a rule with safranin 

 only, sometimes with safranin, gentian violet and orange (i. 



The ovules of Dasylirion are anatropous and furnished 

 with two integuments (fig. 7 and 8) ; the outer one consists, 

 besides of an exterior and interior epiderm, of cells, situated 

 rather irregularly in 2 to 4 rows; towards the chalaza it 

 is much more strongly developed. The inner integument 

 consists of two layers of closely adjacent cells. The micropyle 

 (fig. 1) is formed by the inner integument only, the edges of 

 which are strongly swollen — the cells are larger and the 

 thickness is hère about four cells — and are closely adjacent 

 so that they only leave a narrow slit between them. 



The tissue of the nucellus is small-cellednear the chalaza, 

 but for the rest it consists of large cells with very little 

 protoplasm and apparently very much cell-sap. The more 

 peripheral cells (fig. 1 — 4) are smaller, their cell-walls are 

 perpendicular to the integument, especially near the micro- 

 pyle, but the others are greatly lengthened in the direction 

 of the chalaza so that they hâve become tube-shaped. Thèse 

 tubes are often more or less bent, so that longitudinal sections 

 présent an appearance which is rather diffîcult to disentangle. 

 The swelling of the ovules was in many cases to be ascribed 



Recueil des trav. bot. Néerl. N°. 4. 1905. 15 



