86 



spores had been kept, so that it was impossible to determine be- 

 yond doubt, whether germination had begun and the embryo 

 had been already partially developed before growth had stopped 

 in the spring. In view of these later observations on fern pro- 

 thallia, this is by no means improbable, and if this should be 

 the case, heterospory in Sclaginclla would be advanced one step 

 further in the direction of seed-formation. 



It is certain that further examination of the archegoniates of 

 our arid and semi-arid regions will reveal other adaptations quite 

 as interesting as those already recorded. 

 Stanford University, 

 March, 1904. 



THE POLLEN TUBE IN THE CUCURBITACEAE 

 AND RUBIACEAE 



By Francis E. Lloyh 



In a recently published paper* Longo has given us the very 

 interesting results of his later investigations on the behavior of 

 the pollen tube in the Cucurbitaceae. The close similarity of 

 the facts presented by Longo to those which have been observed 

 by myself in Rubiaceae,t and the parallelism of our conclusions, 

 will, perhaps, warrant a brief comparative statement of our 

 results. 



According to Dr. Longo, the ovary in Cucurbita Pcpo L. is 

 provided with a special conductive tissue which arises, by tan- 

 gential cell-division, " from the epidermis of the placental ridges 

 and extends uninterruptedly from the style, through the three 

 central laminae, to the ovule." The placentae, of course, fuse 

 along their surfaces with one another, so that the layer of con- 

 ductive tissue between any two of them is derived from two epi- 



* Ix>ngo, \\. Ricerche sulle Cucurbitaceae e il significato del percorso inter 

 cellulare (endotropico) del tubetto pollinico. R. Accad. Lincei, Va, 6 : 523-547. 

 //. 1-6. 1903. ["Presented in December, 1902." Hot. Centralb. 95: 114. 

 1904.] 



t Lloyd, F". E. The Comparative Embryology of the Kubiaceae. Memoirs 

 Torrey Botanical Club, 8 : 27-112. /'. 5-/J. 15 1" 1902. 



