SCIENCE-GOSSIP. 



15 



Alter a reference to the desirability of pure and created hygienic conditions will remove from our 



abundant water supplies, Mr. Twelvetrees pointed 

 out in conclusion that disinfection, in the widest 

 sense of the term, involves much more than 

 comparatively limited processes in public disinfect- 

 ing stations, and that nothing short of universally- 



homes the evil presence of disease, and enable 

 the weak and sickly children of our large towns 

 to grow up into " healthy citizens, strong and 

 ready to bear their part bravely in the great battle 

 of life." 



CONTRIBUTIONS TO THE LIFE-HISTORIES OF PLANTS. 



By Thomas Meehax. (*) 



Fellucid Dots in Hypericum. 

 \ X AMY species of Hypericum present small black 

 jots on the stems, leaves or other portions of 

 the 'plant. In H. cotymbosum, Muhl., the stem and 

 lower leaves have these dots profusely scattered 

 over the surface, those on the stem being generally 

 somewhat elongated, after the manner of suber 

 cells as usually seen in the young bark or epi- 

 dermis of woody plants. Examining the series 

 of leaves in succession up the stem, we find the 

 uppermost leaves nearly destitute of black dots, a 

 few being found chiefly near the margin. Starting 

 again from below upward, we find that as we 

 advance, the pellucid dots, wholly absent in the 

 lowermost leaves, begin to be comparatively scarce 

 near the midrib. As they come into existence, the 

 black dots disappear. The pellucid dots increase 

 in numbers with each series of leaves — the black 

 dots seem to give up the ground to the pellucid 

 ones — till, when the much-reduced leaves beneath 

 the flower are reached, scarcely any but the pel- 

 lucid dots are found. They reappear again in 

 numbers on the petals. 



It is singular that though there is an evident 

 correspondence in the increase of pellucid dots and 

 the decrease of the black dots, no genetic relation- 

 ship can be discovered In no instance was there 

 any evidence of a transmutation of a black dot to a 

 pellucid one. 



The dotted structure of other species growing on 

 my ground was therefore examined. These were 

 urn perforatum, H. buckliyi, H. kalmianum of 

 onr country, and H. androsamum, II . calycinum and 

 H. mQUrianum r>i the old world. H. perforatum 

 furnished the most interesting subject for com- 

 panion. The lower leaves, given up wholly to 

 black , had only pellucid riots. 



and in none of these were black dots numerous 

 Indeed, it was only in the uppermost leaves that a 

 lew black d paringly 



distributed near the outer edges. On the petals 

 alio the black dots are sparingly found 



irent from what has been tutted in 

 regard m that the energy productive 



of the black dote U different in degree from that 



productive of pellucid dots. We may further 

 conclude that these varying degrees of growth- 

 energy had but little to do with the differentiation 

 of these two species. One species could readily be 

 transformed to the other as each degree of energy 

 was in control. In H. kalmianum and H. buckleyi 

 pellucid dots are profuse. No trace of black dots 

 could be found. From what has been already 

 noted, they are not to be expected where the 

 pellucid dots abound. 



In the European H. androsamum the whole 

 surface is minutely pellucid-punctate. The mid- 

 rib and veins are also pellucid. At various points 

 along the lines of these veins are, however, small 

 swellings, more or less orbicular, as if they had 

 been originally pellucid dots, and that lines had 

 been thrown out to connect the dots with each 

 other. In H. calycinum there are similar connec- 

 tions, and beside a few scattered pellucid dots ; but 

 these are not round but pyriform, one end tapering 

 into a narrow tail. If a little more prolonged, we 

 shall have just such connections as we find in 

 H. androsamum. In H. moserianum, we find the 

 surface profusely covered with dots, not very 

 pellucid, apparent though they are when held up 

 to a bright light. Some of these are wholly 

 individualized and isolated, but others have sent 

 out a line as yet unconnected, but the great 

 majority have had the lines connected, and have 

 formed a mass of reticulated veinlets unequalled in 

 any otherspecies I have seen. Turning to Hyperium 

 prolificum I find many semi-pellucid dots in the 

 petals, especially near the margin, and some of 

 them elongated, and in a number of cases they have 

 met others and formed an elongated pellucid 

 vein. 



I think these pellucid dots are the initial Steps 

 taken by the plant in the formation of veinlets and 

 veins. It cannot for an instant be conceived that 

 nature first makes a skeleton leaf and then covers 

 il uli parenchymatous tissue. These strcngthen- 

 ing ribs must be constructed out of cell-tissue only 

 U the organism needs them. And this construi 

 tion can only go on under a regularly arranged 

 system. There can be no theoretical rea on againsl 

 1 have taken of the nature and office ol 

 these pellucid dots. 



